PATHOLOGY AND INTERVENTION

IN MUSCULOSKELETAL REHABILITATION

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PATHOLOGY

AND INTERVENTION

IN MUSCULOSKELETAL

REHABILITATION

Editors

David J. Magee, PT, PhD Professor and Associate Dean

Department of Physical Therapy

Faculty of Rehabilitation Medicine

University of Alberta

Edmonton, Alberta, Canada

James E. Zachazewski, PT, OPT, SCS, ATC Clinical Director

Physical Therapy

Massachusetts General Hospital

Boston, Massachusetts

William S. Quillen, PT, PhD, SCS, FACSM Professor

Associate Dean, College of Medicine

Director, School of Physical Therapy and Rehabilitation Sciences

University of South Florida

Tampa, Florida

Editorial Consultant

Bev Evjen Swift Current, Saskatchewan, Canada

ELSEVIER

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PATHOLOGY AND INTERVENTION IN MUSCULOSKELETAL REHABILITATION ISBN: 978- 1-4160-0251-2

Copyright © 2009 by Saunders, an imprint of Elsevier Inc. Photo Copyright © 2009 for Chapter 8 and Chapter 14, will be retained by Diane Lee Photo Copyright © 2009 for Chapter 8 and Chapter 14, will be retained by Linda-Joy Lee

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KNU: LIGAM{NTOUS AND PAULLAR T {NDON INJURI{S Michael M. Reinold, Eric M. Berkson, Peter Asnis, James J. Irrgang, Marc R. Safran, and Freddie H. Fu

Introduction

Successful nonsurgical and surgical management of knee

ligament and patellar tendon injuries requires knowledge

of the functional anatomy and biomechanics of the knee.

This understanding forms the basis for the physical exami­nation of the knee and foundation for treatment options.

When a patient sustains a knee ligament injury or patellar

tendon injury, the clinician must be able to integrate this

information to evaluate the knee and to develop an appro­

priate treatment regimen.

The following chapter presents the scientific back­

ground of the principles of treatment of knee ligament

and patellar tendon injuries . The functional anatomy and

biomechanics of the knee are brought to a clinical level as

the physical examination of the ligamentous injuries are

presented . Specific ligamentous injuries are then discussed

in terms of epidemiology, operative and nonoperative

approaches to treatment, and rehabilitation.

Foundation for Surgical and Nonsurgical Management of Ligament and Patellar Tendon Injuries of the Knee

Functional Anatomy and Biomechanics of the Knee

The tibiofemoral joint is the articulation between the distal

end of the femur and the tibial plateau. The femoral con­

dyles are convex in the anterior and posterior and the

medial and lateral directions. They are separated by the

intercondylar notch, which serves as the site of attachment

528

for the anterior and posterior cruciate ligaments. The width

of the intercondylar notch may be an important consider­

ation for the risk of injury to the cruciate ligaments and

for the development of loss of extension after reconstruc­

tion of the anterior cruciate ligament. The transverse anterior to posterior dimension of the lateral femoral

condyle is greater than that of the medial femoral condyle ( Figure 1 6- 1 ).1 As a result, the lateral femoral condyle pro­

jects farther anteriorly than the medial femoral condyle,

providing a bony buttress to minimize lateral displacement

of the patella. The radjus of curvature of the femoral con­

dyles decreases from anterior to posterior and is shorter

on the medial side than on the lateral side .2 The anterior

to posterior length of the articular surface of the medial

femoral condyle is longer than that of the lateral femoral

condyle. 1 The longer articular surface of the medial femoral

condyle facilitates external rotation of the tibia as the knee

approaches terminal extension.

Static (Passive) Restraints of the Knee

• Joint capsule

• Menisci (2)

• Ligaments, primarily:

o Medial collateral ligament

o Lateral collateral ligament

o Anterior cruciate ligament

o Posterior cruciate ligament

o Posterior oblique ligament

o Arcuate popliteus complex (meniscofemoral ligaments;

ligaments of Humphrey and Wrisberg)

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 529

Dynamic (Active) Restraints of the Knee

• Quadriceps

• Hamstrings

• Gastrocnemius

• Iliotibial band (tensor fascia lata)

• Gracilis

• Sartorius

• Popliteus

The medial tibial plateau is concave from anterior to posterior and from medial to lateral. The lateral tibial pla­teau is convex from anterior to posterior ( Figure 1 6-2 ) . The concavity of the tibial plateaus is increased by the pres­ence of the menisci. The bony configuration of the knee lends little inherent stability. Stability of the knee depends on static and dynamic restraints. The static restraints include the joint capsule, ligaments, and menisci. Dynamic stability is provided by muscles that cross the knee, includ­ing the quadriceps, hamstrings, and gastrocnemius.

The ligamentous restraints of the knee include the collat­eral, cruciate, and capsular ligaments. The medial collateral lig­ament (MeL) is a broad band that runs from the medial epicondyle ofthe femur to insert on the tibia two to three fin­ger widths below the medial joint line ( Figure 1 6-3) . The MeL, which has been described as a thickening of the medial capsule, is divided into deep and superficial layers. The deep MeL is intimately attached to the medial meniscus and con­sists of the tibiomeniscal and femoromeniscal ligaments. The superficial band of the MeL runs from the medial epicondyle to insert distal to the tibial plateau. Because the superficial

TL

Figure 16-1

TL >TM LM>LL

TM

The transverse anterior-posterior dimension of the lateral femoral condyle (TL) is greater than that of the medial femoral condyle (TM).

The anterior to posterior length of the articular surface of the medial femoral condyle (LM) is longer than the anterior to posterior length of the articular surface of the lateral femoral condyle (LL). ( From Cailliet R, editor: Knee pain and disability, ed 3, Philadelphia, 1 992, FA Davis. )

Medial

Figure 16-2 The medial tibial plateau is concave anterior to posterior, whereas the lateral tibial plateau is convex anterior to posterior. (From K..�pandji lA: The physiology of the joints: annotated diagrams of the mechanics of the

human joints, Edinburgh, 1 970, Churchill Livingstone . )

MM

Figure 16-3

Lig. of Humphry Lig. of Wrisbery POP

LCL

Ligamentous structures and menisci at the knee. MM, Medial mcniscus; LM, lateral meniscLls; POp, popliteus tendon; MCL, medial collateral ligament; LCL, lateral collateral ligament. ( From Girgis FG, Marshall JL, Monngem ARS: The cruciate ligaments of the knee joint: anatomical function and experimental analysis, Clin Orthop 1 06:218, 1 975 . )

530 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

band of the MCL is farther from the center of the knee, it is the first ligament injured when a valgus stress is applied. The MCL courses anteriorly as it runs from the femur to the tibia.

The lateral collateral ligament (LCL) is a cordlike struc­ture that runs from the lateral epicondyle of the femur to the fibular head (see Figure 1 6-3 ) . The LCL courses some­what posteriorly as it passes from the femur to the fibular head . It is separated from the lateral meniscus by the popli­teus tendon, which partly explains the increased mobility of the lateral meniscus.

The anterior cruciate ligament (ACL) arises from the tib­ial plateau j ust anterior and medial to the tibial eminence. From the tibia, the ACL courses superiorly, laterally, and posteriorly to insert on the posterior margin of the medial wall of the lateral femoral condyle (Figure 1 6-4) . The ACL has been described as being composed of two bundles: the anteromedial bundle, which is taut in flexion, and the pos­terolateral bundle, which is taut in extension ( Figure 1 6-5 ) .

The posterior cruciate ligament (PCL) arises from the posterior margin of tl1e tibia j ust inferior to the tibial pla­teaL!. From the tibia, the PCL courses superiorly, anteriorly, and medially to insert on the lateral wall of the medial fem­oral condyle ( Figure 1 6-6) . The PCL has been described as consisting of two bands: the anterolateral band, which is taut in flexion , and the posteromedial band, which is taut with the knee in extension.

Figure 16-4 The anterior cruciate ligament arises from the tibial plateau anterior

and medial to the tibial eminence and courses superiorly, laterally, and posteriorly to insert on the medial wall of the lateral femoral condyle. (From Zachazewski JE, Magee D J, QuiJlen WS, editors: Athletic

injuries and rehabilitation, p 625, Philadelphia, 1 996, WE Saunders.)

Figure 16-5 The anterior cruciate ligament is composed of two bundles. The anteromedial bundle (A-A') is taut in flexion. The posterolateral bundle ( B-B') is taut in extension. (From Zachazewski JE, Magee DJ , QuiJlen WS, editors: Athletic injuries and rehabilitation, p 625, Philadelphia, 1 996, WB Saunders.)

A synovial fold covers both cruciate ligaments. The ACL and PCL, therefore, are intrarticular but are considered to be extrasynovial. The predominant blood supply of tl1e cru­ciate ligaments is the middle geniculate artery. Branches of this artery form a plexus within the encompassing synovial

Figure 16-6 . The posterior cruciate ligament arises from the posterior margin of the tibial plateau and courses superiorly, mediaJly, and anteriorly to insert on the lateral waJl of the medial femoral condyle. (From Zachazewski JE, Magee DJ, Quillen WS, editors: Athletic Injuries and Rehabilitation, p 625, Philadelphia, 1 996, WE Saunders.)

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 531

sheath.3 Disruption of this plexus is the source of the hemarthrosis typically seen after ACL injury.

The meniscofemoral ligaments course in a direction sim­ilar to that of the PCL. They arise from the posterior horn of the lateral meniscus and course superiorly and medially to insert on the lateral wall of the medial femoral condyle (see Figure 1 6-3 ) . The ligament of Humphrey lies anterior to the PCL, and the ligament ofWrisberg lies posterior to the PCL. The meniscofemoral ligaments become taut with internal rotation of the tibia.

The posterolateral corner of the knee has a complex anatomy consisting of the biceps femoris, the LCL, and the popliteus complex. Dynamic and static components, including the popliteofibular ligament, the fabellofibular ligament, and the arcuate complex, add to this stability and prevent excessive posterior translation, varus rotation, and posterolateral rotation. The arcuate complex consists of the arcuate ligament, popliteus tendon, LCL, and poste­rior third of the lateral capsule.4 The arcuate ligament arises from the fibular head and LCL to course superiorly and medially to insert along the popliteus tendon and lateral condyle of the femur. The popliteofibular ligament may be present in 98% of knees, but the anatomy of the postero­lateral corner can vary significantly.5 The presence of a fabella, a variable sesamoid bone in the tendinous portion of the gastrocnemius muscle, correlates with the presence of a fabellofibular ligament.

The medial and lateral menisci lie between the tibial plateaus and femoral condyles (see Figure 1 6-3 ) . The menisci improve stability of the knee by increasing the con­cavity of the tibial plateaus. The menisci also absorb shock and distribute weight bearing over a greater surface area.

The outer third of the menisci is vascularized by the mid­dle genicular artery, and the inner third of the menisci is con­sidered to be avascular. Peripheral tears of the menisci, therefore, have the potential to heal and often are repaired surgically; however, tears in the inner third (the avascular zone) do not heal, and partial meniscectomy often is required. Baratz et al.6 demonstrated the effects of a partial or total meniscectomy on the articular contact area and stress in the human knee. Total meniscectomy resulted in a concen­tration of high contact forces on a small area of the tibial pla­teau. Partial meniscectomy resulted in a smaller increase in contact stress. With a total meniscectomy, the increased tibiofemoral contact forces that result may predispose the patient to long-term degenerative changes. Therefore, par­tial meniscectomy is preferred to minimize this risk.

During flexion and extension of the knee, the menisci move posteriorly and anteriorly, respectively (Figure 1 6-7) . This movement is a result of the bony geometry of the tibiofe­moral joint. Posterior movement of the medial meniscus dur­ing flexion also is partly due to tlle insertion of a portion of the semimembranosus into the posterior horn of the medial meniscus. Similarly, fibers from the popliteus tendon insert­ing on the posterior horn of the lateral meniscus pull the

MM fa �

A

Figure 16-7

LM MM�� ��LM B

The menisci move anteriorly with extension (A) and posteriorly with flexion (B). The right knee is shown. MM, Medial meniscus; LM, lateral meniscus. (From Kapandji IA: The physiology of the joints:

annotated diagrams of the mechanics of the human joints, Edinburgh, 1 970, Churchill Livingstone.)

lateral meniscus posteriorly during flexion. Anterior-posterior movement of the lateral meniscus is greater than tllat of the medial meniscus, which reduces the susceptibility of the lateral meniscus to injury. During rotation of the knee, the menisci move relative to the tibial plateaus. During external rotation of the tibia, the medial meniscus moves posteriorly relative to the medial tibial plateau, whereas the lateral menis­cus moves anteriorly relative to tlle lateral tibial plateau. Dur­ing internal rotation of the tibia, movement of the menisci relative to the tibial plateaus is reversed?

Flexion and extension of the knee combine rolling and gliding of the joint surfaces to maintain congruency of these surfaces. During flexion of the knee, the femur rolls posteriorly and glides anteriorly. During extension, the femur rolls anteriorly and glides posteriorly. The combined rolling and gliding of the joint surfaces maintains the fem­oral condyles on the tibial plateaus. Disruption of the nor­mal arthrokinematics of the knee results in increased translation of the joint surfaces, which can lead to progres­sive degenerative changes of the articular surfaces.

Muller7 described the ACL and PCL as a four-bar link­age system that maintains the normal arthrokinematics of the knee (Figure 1 6-8, A). Two of the four bars are the ACL and PCL. The remaining two bars are tlle line con­necting the femoral attachments of the ACL and PCL and the line connecting the tibial attachments of the ACL and PCL. The ACL and PCL are inelastic and maintain a con­stant length as the knee flexes and extends. As a result, the four-bar linkage system controls rolling and gliding of the joint surfaces as tlle knee moves. During flexion, the femur rolls posteriorly. This increases tlle distance between the tibial and femoral insertions of the ACL. Because the ACL cannot lengthen, it guides the femoral condyles ante­riorly (Figure 1 6-8, B). Conversely, during extension of the knee, the femoral condyles roll anteriorly and the distance between the femoral and tibial insertions of the PCL increases. Because the PCL cannot lengthen, it pulls the femoral condyles posteriorly as the knee extends (Figure 1 6-8, C). Disruption of the ACL or PCL disrupts the four-bar linkage system and results in abnormal translation

532 CHAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

A 8 c Figure 16-8 Four-bar linkage system . A, The four bars consist of the anterior cruciate ligament (ACL) (line ab); the posterior cruciate ligament ( PCL) (line cd); the line connecting the femoral attachments of the ACLand PCL (line cb); and the line connecting the tibial attachments of the ACL and PCL (line ad). B, During flexion, the femur rolls posteriorly; this increases the distance between the tibial and femoral insertions of the ACL. Because the ACL cannot lengthen, it guides the femoral condyles anteriorly. C, During extension of the knee, the femoral condyles roll anteriorly and the distance between the femoral and tibial insertions of the PCL increases. Because the PCL cannot lengthen, it pulls the femoral condyles posteriorly as the knee extends. (From Kapandji LA: The physiology of the joints: annotated diagrams of the mechanics of the human joints,

Edinburgh, 1970, Churchill Livingstone. )

of the femoral condyles. Disruption of the normal arthrokine­matics of the knee may lead to repetitive injury of the menisci and joint surfaces and to the development of progressive degenerative changes over time.

Ligamentous Restraints of the Knee The primary restraint to anterior translation of the tibia is the ACL, which provides approximately 85% of the total restraining force to anterior translation of the tibia.8,9 The remaining 1 5% of the restraining ligamentous force to ante­rior displacement of the tibia is provided by the collateral ligaments, the middle portion of the medial and lateral cap­sules, and the iliotibial band (Table 16-1).

Table 1 6-1

Primary and Secondary Restraints of the Knee

Tibial Motion Primary Restraint Secondary Restraints

The primary restraint to posterior displacement of the tibia is the PCL. The PCL provides approximately 85% to 95% of the total restraining force to posterior translation of the tibia.8

The remaining 5% to 1 5% of the total ligamentous restraining force to posterior displacement of the tibia is provided by the collateral ligaments, the posterior portion of the medial and lateral capsules, and the popliteus tendon. The liganlents of Humphrey and Wrisberg also provide restraint to posterior translation of the tibia, and their ability to do so increases with internal rotation of the tibia (see Table 16-1).

The primary restraint to valgus rotation is the MCL.

The ACL and PCL serve as secondary restraints to valgus rotation. When the knee is in full extension, the posterior

Anterior translation Posterior translation

ACL PCL

MCL, LCL; middle third of medial and lateral capsule; iliotibial band

Valgus rotation Varus rotation External rotation Internal rotation

MCL LCL

MCL, LCL ACL, PCL

MCL, LCL; posterior third of medial and lateral capsule; popliteus tendon; anterior

and posterior meniscofemoral ligaments ACL, PCL; posterior capsule when knee is fully extended ACL, PCL; posterior capsule when knee is fully extended

Anterior and posterior meniscofemoral ligaments

From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic injuries and rehabilitation, p 627, Philadelphia, 1 996, WE Saunders. ACL, anterior cruciate ligament; MCL, medial collateral ligament; LCL, lateral collateral ligament; PCL, posterior collateral ligament.

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 533

capsule becomes a significant restraint to valgus rotation (see Table 1 6- 1 ) . For varus rotation, the primary restraint is the LCL, and the ACL and PCL serve as secondary liga­mentous restraints. The restraining force provided by the ACL and PCL, as well as the posterior capsule, increases when the knee is in full extension (see Table 1 6- 1 ) .

External rotation of the tibia is restrained by the collat­eral ligaments, whereas internal rotation is restrained by the cruciatc ligaments and the ligaments of Humphrey and Wrisberg (see Table 1 6- 1 ) .

The quadriceps and hamstrings serve as dynamic stabili­zers of the knee. In doing so, they assist the passive restraints in controlling kinematics of the knee. These muscles work synergistically with the cruciate ligaments to control motion of the knee dynamically. Unopposed contraction of the quadriceps is synergistic to the PCL and antagonistic to the ACL. Conversely, isolated contraction of the hamstrings is synergistic to the ACL and antagonistic to the PCL. It is the­orized that activities that promote co-contraction of the hamstrings and quadriceps minimize tibial translation, and activities of this type have been advocated for rehabilitation of knee ligament injuries.1O Dynamic stabilization of the knee to control abnormal motion depends on muscular strength and endurance, as well as on the development of appropriate neuromuscular control.

Role of Proprioception

Researchers have shown increased interest in the role of proprioception in the prevention and progression of knee injuries. I 1-14 Proprioception has been described as a varia­tion in the sense of touch; it includes the senses of joint motion (kinesthesia) and joint position. Proprioception is mediated by sensory receptors in the skin, musculotendi­nous unit, ligaments, and joint capsule. These sensory receptors transduce mechanical deformation to a neural sig­nal, which modulates conscious and unconscious responses. It has been hypothesized that proprioception is important for providing smooth, coordinated movement and for pro­tecting and dynamically stabilizing the knee.13,15-17

Mechanoreceptors in the knee may mediate protective reflexes. Solomon ow et al.13 described an ACL-hamstring reflex arc in anesthetized cats. High loading of the ACL resulted in increased electromyographic (EMG) activity in the hamstrings, with electrical silence in the quadriceps. The increase in hamstring EMG activity was not evident when low to moderate loads were applied to the ACL. It originally was thought that dle ACL-hamstring reflex arc protected the ACL during high loading conditions. However, recent studies have shown dlat this reflex has a relatively long latency in humans; therefore, radler than being a protective reflex, it may be important for updating motor programs. 18

Other proprioceptive reflexes originating from the joint capsule or musculotendjnous unit probably exjst. This was

demonstrated by Solomonow et al.,13 who reported increased hamstring EMG activity in a patient with an ACL-deficient knee during maximum slow speed isokinetic testing of the quadriceps. The increased hamstring EMG activity occurred simultaneously with anterior subluxation of dle tibia at approximately 40° knee flexion and was asso­ciated with a sharp decrease in quadriceps torque and inhi­bition of quadriceps EMG activity. Because the ACL was ruptured, reflex contraction of dle hamstrings could not have been mediated by receptors originating in the ACL. It was proposed that this reflex contraction is mediated by receptors in the joint capsule or hamstring muscles.

Several clinical studies have evaluated proprioception in terms of threshold to detection of passive motion and repro­duction of passive joint position. Barrack et al. II demon­strated deficits in threshold to detection of passive motion in subjects with a unilateral ACL-deficient knee. Barrettl6 demonstrated high correlations between measurements of proprioception and function ( r = 0.84) and patient satisfac­tion ( r = 0.90) in 45 patients who had undergone ACL reconstruction. Standard knee scores and cbnical examina­tion results correlated poorly with the patient's own opinion and the results of functional tests. Lephart et al.14 studied the threshold to detection of passive movement in patients who had undergone ACL reconstruction. Testing was per­formed at 1 5° and 45° flexion. Three trials were performed, moving into flerion and extension. The results indicated that the threshold to detection of passive movement was less sensitive in the reconstructed knee than the noninvolved knee. Also, the threshold to detection of passive motion was more sensitive in both the reconstructed knee and the normal knee at 1 5° flexion than at 45° flexion. Sensitivity to detection of passive motion was enhanced by the use of a neoprene sleeve, which has implications for bracing after ACL injury and/or reconstruction. Use of a sleeve or com­pressive wrap or garment may help the patient develop a greater sense of perception of the knee during rehabilitation and progressive activity.

Injury to the knee may result in abnormal sensory feed­back and altered neuromuscular control, which may lead to recurrent injury. Proprioceptive training after knee injury and/or surgery should attempt to maximize the use of sen­sory information mediated by the ligaments, joint capsule, and/or musculotendinous unit to stabilize the joint dynami­cally. Proprioceptive training requires repetition to develop motor control of abnormal joint motion and may be enhanced with the use ofEMG biofeedback. Initially, control of abnormal joint motion requires conscious effort. Through repetitive training, motor control of abnormal movement becomes automatic and occurs subconsciously. It should be noted, however, that the extent to which an individual can develop neuromuscular control of abnormal joint motion to stabilize dle knee dynamically currently is unknown. Fur­ther research is required to determine the effectiveness of proprioceptive training to stabilize the knee dynamically.

534 CHAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

Biomechanics of Exercise

Open kinetic chain (OKC) exercise is exercise in which the distal segment is free to move, resulting in isolated move­ment at a given joint. At the knee, OKC exercise results in isolated flexion and extension. OKC knee extension is a result of isolated contraction of the quadriceps, and open chain knee flexion occurs as a result of isolated contraction of the hamstrings. Baratta et al.17 and Draganich et al.19

demonstrated low levels of co-activation of the quadriceps and hamstrings during open chain knee extension. It is hypothesized that the hamstrings become active during the terminal range of extension to decelerate the knee and act as a synergist to the ACL to minimize anterior tibial translation produced by contraction of the quadriceps. During open chain knee extension, the flexion moment arm increases as the knee is extended from 90° flexion to full extension (0°). This requires increasing quadriceps and patellar tendon tension, which can increase the load on the patellofemoral and tibiofemoral joints.

During closed kinetic chain (CKC) exercises, the distal segment is relatively fixed; therefore movement at one joint results in simultaneous movement of all other joints in the kinetic chain in a predictable manner. The lower extremity functions as a closed kinetic chain when a person squats over the fixed foot, resulting in simultaneous movement of the ankle, knee, and hip. CKC exercise for the lower extremity results in contraction of muscles throughout the lower extremity. During CKC exercises for the lower extremity, the flexion moment arms at the knee and hip increase as the squat is performed, and increased force of contraction of the quadriceps and hamstrings is required to control the knee and hip, respectively.

v (rAl' -. , I Quadriceps neutral

angle 60-75°

A B Figure 16-9

OKC and CKC exercises have different effects on tibial translation and ligamentous strain and load. During active OKC knee extension, the shear component produced by unopposed contraction of the quadriceps depends on the angle of knee flexion (Figure 16-9). Sawhney et al.20 inves­tigated the effects of isometric quadriceps contraction on tibial translation in subjects with an intact knee. Tibial translation was measured with the KT1000 Ligament Arth­rometer (MEDmetric, San Diego, CA) at 30°, 45°, 60°, and 75° flexion. Open chain isometric quadriceps contrac­tion against 10 pounds (4.5 kg) of resistance applied to the distal aspect of the leg resulted in anterior tibial transla­tion at 30° and 45° flexion. No significant tibial translation occurred at 60° or 75° flexion. It was determined that the quadriceps-neutral Q angle (i.e., the angle at which quadri­ceps contraction produces no anterior or posterior tibial translation) occurs at 60° to 75° flexion (see Figure 16-9, A).

OKC knee extension at angles less than the quadriceps­neutral position results in anterior translation of the tibia. This was demonstrated by Grood et al.9 in intact cadaveric knees. Anterior translation of the tibia during OKC knee extension increased with loading of the quadriceps at angles less than 60° flexion. Sectioning of the ACL increased anterior translation during loaded and unloaded open chain knee extension. Anterior tibial translation pro­duced by the quadriceps at knee flexion angles less than the quadriceps-neutral angle is a result of the anteriorly directed shear component of the patellar tendon force (see Figure 16-9, B). OKC knee extension at knee flexion angles greater than the quadriceps-neutral position results in posterior tibial translation. This is the result of a posteri­orly directed shear component of the patellar tendon force at these angles of knee flexion (see Figure 16-9, C).

20°

c

During open chain knee extension, tibial translation is a function of the shear force produced by the patellar tendon. A, Quadriceps neutral position. The patellar tendon force is perpendicular to the tibial plateaus and results in compression of the joint surfaces without shear. B, At flexion angles less than the angle of the quadriceps neutral position, orientation of the patellar tendon produces anterior shear of the tibia. C, At angles greater than the angle of the quadriceps neutral position, patellar tendon force causes a posterior shear of the tibia. ( From Daniel DM, Stone ML, Barnett P, Sachs R: Use of the quadriceps active test to diagnose posterior cruciate ligament disruption and measure posterior laxity of the knee, J Bone

Joint Sut;g Am 70:386-39 1 , 1 98 8 . )

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 535

OKC knee flexion is produced by isolated contraction of the hamstrings. This has been shown to result in posterior translation of the tibia and was demonstrated by Lutz et al ./ l who found posterior tibial shear forces during iso­metric open chain knee flexion at 30°, 60°, and 90° knee flexion. The posterior shear force increased as flexion pro­gressed from 30° to 90° flexion.

Several methods of biomechanical analysis have been used to study rehabilitation of the knee, including cadav­eric, EMG, kinematic, kinetic, mathematical modeling, and in vivo strain gauge measurements. These studjes are best evaluated by delineating the findings according to the tissue or structure examined, such as the ACL, the PCL, and the patellofemoral joint.

Anterior Cruciate Ligament Most biomechanical research on rehabilitation of the knee has focused on the ACL. After years of theoretical and anec­dotal assumptions, researchers now are better able to scruti­nize more closely the efficacy of OKC and CKC exercises. Markolf et al.22 examined the effect of compressive loads on cadaveric Knees to simulate body weight. These authors reported that compressive forces reduce strain on the ACL, compared to OKC exercises, thus providing a protective mechanism. Fleming et al.23 investigated this theory using in vivo strain gauge measurements in the ACL. This method allows direct measurement of ACL strain during activity. The authors noted that strain on the ACL increased from -2% during non-weight-bearing to 2.1 % in a weight-bearing posi­tion. Although an increase in ACL strllin was observed in a weight-bearing position, it still is unclear whether a 2% strain is detrimental to a healing ACL graft. Clinical experience has shown that early weight bearing does not result in poor func­tional outcomes in postoperative ACL reconstructions.

CKC exercises have also been theorized to reduce ACL strain by providing co-contraction of the hamstrings and quadriceps. Wilk et al 24 examined the EMG activity of the quadriceps and hamstrings during the CKC squat and leg press and the OKC knee extension . These authors noted that co-contraction occurred from 30° to 0°, during the ascent phase of the squat, when the body is positioned directly over the knees and feet, but it did not occur at other ranges of motion or during the eKC leg press or OKC knee extension. Therefore, not all CKC exercises pro­duce a co-contraction of the quadriceps and hamstrings. Rather, several factors appear to affect muscle activation during CKC exercises, including the knee flexion angle, body position relative to the knee, and the direction of movement ( ascending or descending) . Clinically, exercises performed in an upright and weight-bearing position with the knee flexed to approximately 30° (e .g., squats and lat­eral lunges) may be used during knee rehabilitation to pro­mote co-contraction of the quadriceps and hamstrings.

Wilk et al .24 also used mathematical modeling to estimate the shear forces at the tibiofemoral joint during the squat,

+1750 r---------------------,

+1500

� +1250 o � +1000 � t'J +750 a: fi? a: .. w I Ul

+500

+250

25 36 47 58 69 80 91 102 91 80 69 58 47 36 25 14 1------ Knee Flexing ------------> 1------- Knee Extending ------------> I

KNEE FLEXION ANGLE

Figure 16-10 Tibiofemoral shear forces observed throughout the range of motion during closed kinetic chair squat (filled triangles) and leg press (small

points) exercises and open kinetic chain knee extension exercises (open

circles). ( From Wilk KE, Escamilla RF, Fleisig GS et al : A comparison of tibiofemoral joint forces and electromyographic activity during open and closed kinetic chain exercises, Am] Sports Med 24:522, 1 996.)

leg press, and knee extension exercise ( Figure 16-10). The authors reported that a posterior tibiofemoral shear force was observed during the entire range of motion during both the CKC squat and leg press ( peak, 1500 newtons [N]), and during deep angles of OKC knee extension from 100° to 40° (peak, 900 N ) . Anterior tibiofemoral shear force (peak, 250 N), and theoretically ACL strain, was observed during the OKC knee extension exercise from 40° to 100.

Similar to the results of Wilk et al./4 Beynnon et al . ,25 using in vivo strllin gauge measurements, found that the greatest amount of ACL strain (2.8%) occurred during 40° to 0° OKC knee extension. This strain was found to increase significantly in a linear fashion with the application of an external 45 Newton boot (3.8% ). However, the authors also reported an ACL strain of 3.6% during tlle CKC squat exercise. In contrast, application of external loading did not significantly increase the amount of strain on the ACL (4%).

Based on the findings of Fleming et al.2\ Wilk et al.,z4 and Beynnon et al . ,25 both OKC and CKC exercises should be performed during rehabilitation of a reconstructed ACL, although the patient often is limited to 90° to 40° during the OKC knee extension when heavy resistance is applied.

The bicycle and stair climbers also are commonly used during ACL rehabilitation . FlenUng et al.26 analyzed six dif­ferent bicycle ridjng condjtions, maillpulating speed and power. These authors found no significant differences among these conditions (minimal mean ACL strajn of 1.7% ). The greatest amount of strain was observed when the knee reached the greatest amount of extension. Simi­larly, Fleming et al.2? analyzed two cadences of stair climb­ing (80 and 112 steps per minute) and noted a similar 2.7%

536 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

Table 1 6-2

In Vivo Strain on the Anterior Cruciate Ligament

Isometric quadriceps contraction at 15° Squatting with resistance Active knee flexion with resistance Lachman's test (150 N of anterior shear at 30°) Squatting without resistance Active knee flexion without resistance Quadriceps and hamstring co-contraction at 15° Isometric quadriceps contraction at 30° Stair climbing Anterior drawer test (150 N anterior shear at 90°) Stationary bicycle Quadriceps and hamstrings co-contraction at 30° Passive knee range of motion Isometric quadriceps contraction at 60° and 90° Quadriceps and hamstrings co-contraction at 60°

and 90°

4.4% 4.0% 3.8% 3.7% 3.6% 2.8% 2.7% 2.7% 2.7% 1.8% 1 .7% 0.4% 0.1% 0.0% 0.0%

Isometric hamsu'ing contraction at 30°, 60°, and 90° 0.0%

Modified from Fleming Be, Beynnon B D , Renstrom PA et al: The strain behavior of the anterior cruciate ligament during stair climbing: an in vivo study, Arthroscopy 1 5 : 1 85- 1 9 1 , 1 999.

strain on the ACL. Again, the greatest strain was observed during terminal knee extension. Therefore, both bicycling and stair climbing are safe exercises to perform that put low strain on the ACL compared to other rehabilitation exercises (Table 16-2). Furthermore, the finding that the greatest amount of strain occurred as the knee moved into terminal knee extension was similar to the results seen by Wilk et aI .24 and Beynnon et al .25 during OKC and CKC exercises.

Posterior Cruciate Ligament Historically, rehabilitation after injury to the PCL has had mixed results. Poor functional outcomes have often been attributed to residual laxity after surgical reconstruction. The biomechanics of the tibiofemoral joint during exercise must be understood so that the rehabilitative process does not have deleterious effects on the PCL.

Posterior tibiofemoral shear forces that occur during specific activities, such as level walking,28 ascending and descending stairs,z9 and resisted knee flexion exercises,30,3 1

have been documented.32 Level walking and descending stairs have a relatively low posterior tibiofemoral shear force, 0.4 x body weight ( BW) and 0.6 x BW, respectively (Table 16-3). However, high posterior shear force has been noted during several commonly performed activities of daily living, such as climbing stairs ( 1 .7 x BW at 45° knee flexion )29,33 and squatting (3.6 x BW at 140° knee flex­ion) , which may have an effect on residual laxity after sur­gery. Further studies have shown that isometric knee flexion at 45° places a posterior shear force of 1.1 x BW on the tibiofemoral joint.3 1

Table 16-3

Posterior Tibiofemoral Shear Forces

Force Knee Angle ( x Body

Source Activity (Degrees) Weight)

Kaufman 30 60° /sec flexion 75 1.7 isokinetic

1 80° /sec flexion 75 1 .4 isokinetic

Morrison28 Level walking 5 0.4 Morrison29 Descending 5 0.6

stairs Ascending stairs 45 1.7

Smidt3 1 Isometric flexion 45 1.1

Tremendous shear forces on both the PCL and the tibio­femoral joint occur during OKC resisted knee flexion. Poste­rior tibial displacement is attributed to the high EMG activity of the hamstring muscles during resistive knee flexion. Lutz et aI .21 reported a maximwn shear force of 1780 N at 90°, 1526 N at 60°, and 939 N at 30° during isometric knee flex­ion. Kaufman et aI.30 also noted a PCL load of 1.7 x BW at 75° during isokinetic knee flexion exercise. Because PCL stress increases with the knee flexion angle, isolated OKC knee flexion exercises should be avoided for at least 8 weeks after surgery or, in patients who did not undergo surgery, until symptoms subside .

Excessive stress on the PCL has also been observed dur­ing deeper angles of OKC knee extension. Several studies have proven that resisted knee extension at 90° flexion causes a posterior tibiofemoral shear and potential stress on the PCL. 1 3 ,20,21 ,24,34 Wilk et al.24 documented a poste-rior shear force from 100° to 40° with resisted OKC knee extension . The greatest amount of stress on the PCL was seen at angles of 85° to 95° during knee flexion. Con­versely, the lowest amount of posterior shear force occurred from 60° to 0° of resisted knee extension 24 Kaufman et al.30 also reported that posterior shear forces are exerted until 50° to 55° knee flexion . Jurist and Otis34 documented stress on the PCL at 60° flexion during an isometric knee extension exercise when resistance is applied at the proximal tibia. To reduce the excessive posterior shear force on the PCL, OKC resisted knee extension should be performed from 60° to 0° .32

The stress applied to the PCL during CKC exercises depends on the knee flexion angle produced during the exercise. Wilk et a1.24,35 reported an increase in posterior shear force as the knee flexion angle increased during CKC exerCise. Stuart et aI .36 also documented a linear increase in posterior shear force from 40° to 100° knee flex­ion during the front squat maneuver. Therefore, to reduce PCL stress during CKC exercises, leg presses and squats should be performed from 0° to 60° knee flexion.32

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 537

Patel/ofemoral Joint The effects of OKC versus CKC exercises on the patellofe­moral joint must be considered in a rehabilitation regimen after knee ligament injury and/or surgery. The patellofe­moral joint consists of the articulation between .the patella and the distal end of the femur. The patella is em bedded in the knee extensor mechanism and is the largest sesamoid bone in the body. Proximally, the quadriceps inserts into the patella through the quadriceps tendon. Distally, the patella is connected to the tibia through the patellar tendon. The patella protects the anterior aspect of the knee, increases the effective moment arm of the knee extensor mechanism, and centralizes the divergent forces produced by the quadri­ceps. The tendency of the patella to sublux laterally (pro­duced by the Q [q uadriceps] angle, the vastus lateralis, and the lateral retinacular structures) must be counterbalanced by the oblique fibers of the vastus medialis. Maintaining this balance is crucial to normal function of the knee extensor mechanism.

The patella is a triangular bone with the base directed superiorly and the apex clirected inferiorly. The patella is described as having three facets on its posterior aspect. A central ridge that runs from superior to inferior divides the patella into medial and lateral facets. The odd facet lies on the medial border of the patella and engages the femur only during the extreme range of flexion. The posterior margin of the patella is covered by a thick layer of articular cartilage, which is thicker centrally than peripherally. This layer of articular cartilage is thicker than at any other joint in the body, perhaps up to 5 mm thick.37 It is important for reducing friction and aiding lubrication of the patellofemoral joint.

The stability of the patellofemoral joint depends on static and dynamic restraints. Static restraints consist of the shape

Figure 16-11

of the patellofemoral joint and the medial and lateral patellofe­moral ligaments. The lateral femoral condyle projects farther anteriorly than the meclial femoral condyle and serves as a but­tress to minimize lateral clisplacement of the patella. Dynamic stability of the patellofemoral joint is provided by dle quadri­ceps. The vastlls meclialis oblique (VMO) and medial retinac­ulum provide medial stabilization of the patella. The vastus lateralis, lateral retinaculum, and iliotibial band pull the patella laterally. The Q angle is dle angle formed by lines d1at connect the anterior superior iliac spine (ASIS) to the midpatdla and the midpatella to d1e tibial tubercle. The Q angle results in lat­eral displacement of the patella when the quadriceps contracts. Lateral displacement of the patella is dynamically resisted by the VMO and meclial retinaculum. Weakness of dle VMO allows dle patella to track laterally. In adclition, tightness of the lateral retinaculum and overpull from the vaSU1S lateralis and iliotibial band can result in lateral displacement of the patella.

Prevention and/or treatment of patellofemoral symp­toms after knee ligament injury or surgery should seek to maintain or restore dle balance of dle medial and lateral sta­bilizers of the patellofemoral joint.

Hungerford and Barry38 described the patellofemoral con­tact pattern as the knee moves wough a full range of motion ( Figure 16-11). The patella initially makes contact with the femur in dle trochlear groove at approximately 200 flexion. Initial contact is between the trochlear groove and dle inferior pole of the patella. As flexion progresses, the contact area on the patella progresses superiorly, so dlat by 900 flexion, dle entire articular surface of the patella, except for the odd medial facet, has articulated with the femur. As flexion continues beyond 900, dle quadriceps tendon articulates widl the troch­lear groove and the patella moves into the intercondylar notch area of the femur. At full flexion, dle odd medial facet and

Patellofcmoral contact pattern. Initial contact between the trochlear groove and the inferior pole of the patella occurs at approximately 200 flexion. As flexion progresses, the area of contact migrates superiorly so that by 900 flexion, the entire articular surface of the patella except for the odd facet has

articulated with the trochlear groove. At full flexion, the odd medial facet and lateral facet articulate

with the intercondylar notch. (From Magee D J : Orthopedic Physical Assessment, ed 3, p 729, St. Louis, 2007, Saunders . )

538 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

lateral facet of the patella articulate with the intercondylar notch. The odd medial facet articulates with the femur only at the end range of flexion.

A knowledge of the patellofemoral contact pattern is use­ful for determining the limits of motion when patients with patellofemoral symptoms perform OKC and CKC exercises. Generally, exercises should be performed in the pain-Jree and

crepitus-free range of motion. It should also be noted that the patellofemoral contact area increases from 20° to 90°

flexion. This increase helps distribute patellofemoral joint reaction forces over a larger area to reduce patellofemoral contact stress per unit of area. (Chapter 1 8 presents a more detailed discussion of the impact of patellofemoral forces and mechanics during rehabilitation and activity.)

Alterations in the Q angle often are associated with patello­femoral disorders. They may alter the contact areas and thus the amount of joint reaction forces of the pateUofemoral joint. Huberti and Hayes39 examined the in vitro patellofemoral contact pressures at various degrees of knee flexion from 20°

to 120° . The maximum contact area occurred at 90° knee flex­ion, where contact pressure was estimated to be 6.5 x BW. An increase or decrease in the Q angle of 1 0° resulted in increased maximlUTI contact pressure and a smaller total area of contact throughout the range of motion. Clinicians can use this infor­mation in prescribing rehabilitation interventions to ensure that exercises are performed in ranges of motion that place minimal strain on damaged structures.

PateUofemoral joint reaction force is a function of quadri­ceps and patellar tendon tension and of the angle formed between the quadriceps and patellar tendons (Figure 1 6- 1 2 ).

Patellar tendon force

Figure 16-12

Patellofemoral joint reaction force

Patellofemoral joint reaction force . This is a function of patellar and quadriceps tendon tension and the angle formed between the quadriceps and patellar tendons. This force increases with increasing patellar and quadriceps tendon tension and an increasing angle of knee flexion. ( From Zachazewski JE, Magee D J, Quillen WS, editors: Athletic injuries

and rehabilitation, p 633, Philadelphia, 1 996, WE Saunders . )

This force compresses the pateUofemoral joint, with increasing patellar and quadriceps tendon tension and an increasing angle of knee flexion. Patellofemoral joint reaction forces dur­ing functional CKC activities were calculated by Reilly and Martens40 and were found to be 0.5 x BW during level walk­ing, 3.3 x BW on stairs, and 7.8 x BW during a full squat. These results are consistent with activities that increase patel­lofemoral symptoms.

OKC and CKC exercises produce different effects on patel­lofemoral joint reaction force and contact stress per unit area. During open chain knee extension, the flexion moment arm for the knee increases as the knee is extended from 900 flexion to full extension (0°), which results in increased quadriceps and patellar tendon tension and increasing pateUofemoral joint reaction forces. For CKC exercises, the flexion moment arm of the knee increases as the angle of knee flexion increases. In the case of OKC exercises, the patellofemoral joint reaction forces may be concentrated in a relatively small contact area, resulting in larger contact stresses per unit area; this can create forces that ultin1ately result in symptoms such as pain and possibly degenerative change. Conversely, for CKC exercises, the flex­ion moment arm of the knee increases as the knee flexion angle increases. Greater quadriceps and patellar tendon tension is required to counteract the increasing flexion moment ann. By controlling the position of the foot, ankle, knee, and hip in this weight-bearing position, it may be possible to influence the position and "tracking" of the pateUa, which results in increasing patellofemoral joint reaction force as the knee flexes. This force is distributed over a larger patellofemoral contact area, minin1izing the increase in contact stress per unit area.

The effectiveness and safety of OKC and CKC exercises during patellofemoral rehabilitation have been heavily scru­tinized in recent years. CKC exercises replicate functional activities, such as ascending and descending stairs, but OKC exercises often are important for isolated muscle strengthening when specific muscle weakness is present.4 J

Steinkamp et al.42 analyzed patellofemoral joint biome­chanics during the leg press and extension exercises in 20 nor­mal subjects. Patellofemoral joint reaction force, stress, and moments were calculated during both exercises. At 00 to 460

knee flexion, the patellofemoral joint reaction force was less during the CKC leg press. Conversely, at 500 to 900 knee flex­ion, joint reaction forces were lower during the OKC knee extension exercise. Joint reaction forces were minimal at 900

knee flexion during the knee extension exercise. Similar find­ings have been reported by Escamilla et al.,43 who studied patellofemoral compressive forces during the OKC knee extension and the CKC leg press and vertical squat. OKC knee extension rroduced significantly greater forces at angles less than 570 knee flexion, whereas bOtll CKC activities produced significantly greater forces at knee angles greater than 850•

The results of these two studies should influence clinicians' choice of tlle range of motion in which they have tlleir patients perform OKC and CKC exercises to develop quadriceps strength while protecting the patellofemoral joint.

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 539

In analyzing the biomechanics of the OKC knee exten­sion, Grood et al.9 reported that quadriceps force was great­est near full knee extension and increased with the addition of external loading. The small patellofemoral contact area observed near full extension, as previously discl)ssed, and the increased amount of quadriceps force generated at these angles may make the patellofemoral joint more susceptible to injury. At lower angles of extension (closer to full extension, or 0°), a greater magnitude of quadriceps force is focused onto a more condensed location on the patella. Therefore, if the results of Steinkamp et al . ,42 Escamilla et a l . ,43 and Grood et al.9 are applied, it appears that during OKC knee extension, as the contact area of the patellofemoral joint decreases, the force of quadriceps pull subsequently increases; as a result, a large magnitude of patellofemoral contact stress is applied to a focal point on the patella while it is seated in the trochlear groove, in a position to articulate with the femur. In contrast, during CKC exercises, the quad­riceps force increases as the knee continues into flexion. However, the area of patellofemoral contact also increases as the knee flexes, leading to a wider dissipation of contact stress over a larger surface area.

Recently, Witvrouw et al.44 prospectively studied the effi­cacy of OKC and CKC exercises during nonoperative patel­lofemoral rehabilitation . Sixty patients participated in a 5-week exercise program consisting of either OKC or CKC exercises. Subjective pain scores, functional ability, quadri­ceps and hamstring peak torque, and hamstring, quadriceps, and gastrocnemius flexibility all were recorded before and after rehabilitation and at 3 months after the program ended. Both treatment groups reported a significant decrease in pain, increase in muscle strengtll, and increase in functional performance at 3 months after intervention.

The stucties seem to show that bOtll OKC and CKC exer­cises can be used to maximize tlle outcomes for patellofemoral patients if they are performed within a safe range of motion. Exercises prescribed by tlle clinician should be individualized according to tlle patient's needs and tlle clinician's assessment. IfCKC exercises are less painfid tllan OKC exercises, tllen that form of muscular training is encouraged . In adctition, for post­operative patients, regions of articular cartilage wear must be considered carefidly before an exercise program is designed. Clinicians most often al low open kinetic exercises, such as knee extension at 90° to 40° knee flexion. This range of motion provides the lowest patellofemoral joint reaction forces while providing the greatest amount of patellofemoral contact area. CKC exercises, such as tlle leg press, vertical squats, lateral step-ups, and wall squats (slides), are performed initially at 0° to 16° and tllen progressed to 0° to 30°, where patellofemoral joint reaction forces are lower. As the patient's symptoms subside, the ranges of motion performed are pro­gressed to allow greater muscle strengtllening in larger ranges. Exercises are progressed based on the patient's subjective reports of symptoms and the clinical assessment of swelling, range of motion, and painfitl crepitus.

Examination of the Knee

Subjective Assessment and History

A tl1orough history and physical examination are essential for making the correct diagnosis and determining appropriate treatment. Most injuries about tlle knee can be diagnosed witll a tl10rough clinical evaluation , which often can elimi­nate the need for advanced imaging. (A filII discussion of tlle history and physical examination can be found in volume 1 of tl1is series, Orthopedic Physical Assessment, Chapter 12.)

The history can help determine the patient's activity level before injury and expectations after recovery. This can help in the planning and timing of treatment and in ensuring tllat patients have a realistic expectation of the outcome after tl1e injury.

The clinician first must determine whether the injury is of traumatic origin . With traumatic injuries, the patient should be asked about the mechanism of injury and tlle location of the pain . This information provides a clue as to which anatomic structures are at risk. The examiner should determine whether the foot was planted, whetller tlle injury was a twisting injury, whether the injury resulted from ctirect contact, and the ctirection of the forces involved. It is important to determine whether the patient had injured tl1e same knee before and if so, how it was trea­ted. Was the patient able to leave the scene unassisted or was assistance required? This may indicate tl1e severity of the injury. The patient may be able to relate hearing or feel­ing a pop at the time of injury, which may indicate a cruci­ate ligament tear or osteochondral fracture. Determining whether any deformity was present that may have been reduced before the patient was evaluated is helpful in diag­nosing a patellar or tibiofemoral dislocation or periarticular fracture. Determining the time course of swelling of tl1e knee after injury also is helpful, because an acute effusion or hemarthrosis may differentiate an intra-articular fracture or torn cruciate ligament from a peripheral meniscal tear or patellar ctislocation .

The same history i s required for a subacute o r chroni­cally dysfunctional knee, because the injury may have been initiated by a traumatic event but never treated . The exam­iner must determine when the symptoms began in relation to a traumatic event. The patient must relate whether the primary complaint is popping or clicking, giving way ( insta­bility) , locking, pain, or swelling. The relationship between activity and the patient's symptoms can also be helpful in determining tlle cause of the problem. Pain on takeoff ( and, to a lesser extent, landing) in jumping often is due to extensor mechanism problems (patella, patellar tendon, quadriceps tendon), whereas instability on landing suggests ACL insufficiency or quadriceps weakness. A history of popping or clicking frequently is elicited, and these sounds can be caused by a variety of conditions, both pathological and normal .

540 CHAPTER 1 6 • Knee: ligamentous and Patellar Tendon Injuries

Instability often is described as giving way, sliding, slip­ping out of socket, buckling, or the sensation that the knee may give out. Giving way usually indicates intra-articular pathology, including a displaced meniscal tear or cruciate ligament injury, resulting in a loose body or rotary instabil­ity. Impending giving way may be due to patellar subluxa­tion or weakness of the extensor mechanism. Most patients with chronic rotatory instability can ambulate and perform activities of daiJy living without pain or instability. These patients complain of buckling during activities such as running, jumping, pivoting, or cutting. True locking is a mechanical block to full extension with uninhibited flex­ion, and it usually indicates a displaced meniscal tear. Other causes of locking include loose bodies, joint effusion, ham­string spasm, posterior capsulitis, and sometimes disruption of the quadriceps mechanism.

A history of swelling commonly is obtained after an injury; however, the time from injury to the onset of swell ing and the location and amount of swelling should be determined, as well as its response to rest, activity, and medications. The development of a large, acute hemarthro­sis within 2 to 6 hours after injury occurs secondary to an ACL rupture approximately 70% of the time,45 although it also may be due to an intra-articular or osteochondral fracture. Alternatively, an acute hemarthrosis may be due to patellar dislocation; however, because the capsule is torn, the swelling usually is not as large as with a cruciate liga­ment disruption or fracture. An effusion that develops 1 or more days after injury usually is a hydrarthrosis, which occurs secondary to a meniscal tear, synovitis, or sympa­thetic effusion. Chronic synovitis and its attendant effusion indicate intra-articular inflammation. It usually is caused by a meniscal tear, advanced chondromalacia patella (patellar dysfunction, or excessive lateral patellar compression syn­drome), rotatory instabil ity, or loose bodies. The differen­tial diagnosis must also include pigmented villonodular synovitis, osteochondritis dissecans, inflammatory and/or rheumatological arthritis, and other causes of synovitis.

Physical Examination

A thorough physical examination complements a good his­tory. (We recommend that the reader review Chapter 12 in volume 1 of this series, Orthopedic Physical Assessment, for a detailed explanation of how to complete various physical examination techniques associated with examination of the knee . ) Clinicians not only must be able to perform a physical examination accurately, they must understand the rationale for using specific examination techniques to diag­nose ligamentous instability. This understanding is critical for an accurate, efficient patient examination .

The motion resulting from a clinical test in a relaxed patient depends on the position of the limb at the start of the test, the point of application and direction of the force, and the examiner's ability to detect displacement. Manual

examination of the knee compares the two sides to differen­tiate normal laxity from pathological instability. In a normal patient, left to right, side-to-side differences usually are negligible, therefore an internal control often exists for most patients. Most knee ligament tests assess for patholog­ical motion by stressing a specific ligament or ligament complex. The motion detected during this examination depends on whether the primary or the secondary restraints have been disrupted (see Table 16- 1). When a primary restraint is disrupted, pathological motion occurs, but its extent is limited by the remaining structures, called second­

ary restraints. Disruption of a secondary restraint does not result in pathological motion if the primary restraint is intact; however, disruption of the secondary restraint when the primary restraint is disrupted enhances pathological motion. For all clinical laxity tests, the femur is held steady and the tibial translation or rotation (joint space opening) is measured. A summary of the examination of the knee is presented in Box 16-1.

Specific Tests

Medial Collateral Ligament Abduction (Valgus Stress) Test. The valgus stress test

assesses the integrity of the MCL and medial instability in one plane only. With the patient supine and the leg held in slight external rotation, a gap opens in the medial joint line when a valgus stress is applied across the knee (Figure 16-13). The examiner's hand is placed on the lateral joint line to feel for opening of the medial joint line when valgus stress is applied from the lateral aspect of the knee. The knee is tested first in full extension and again in 20° to 30° knee flexion. It is imperative to examine both knees, because some ligamen­tous laxity may be normal in some individuals. The severity of injury to the MCL and associated structures can be deter­mined by the amount of medial joint line opening in extension and slight flexion. With the knee in full extension, capsular and other secondary restraints resist valgus stress, even when the MCL is disrupted. Flexion of the knee to approximately 30° relaxes the secondary restraints for primary testing of the MCL.

If increased medial joint line opening is seen in the affected knee at 20° to 30° flexion, the posterior oblique ligament and posteromedial capsule may be injured.

If excessive medial joint opening is seen in full extension, a more severe injury to the secondary structures must be assumed. Medial joint line opening with the knee in full extension indicates injury to the MCL (superficial and deep fibers), posterior oblique ligament, ACL, PCL, posterome­dial capsule, medial quadriceps expansion and retinaculum, and semimembranosus. With this more severe injury, the results of one or more rotatory instability tests are also positive.

MCL injuries are graded as first, second, or third degree. A grade I MCL injury is indicated by pain and tenderness

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 541

Box 1 6-1 Physical Examination of the Knee

Standing Position

• Mechanical alignment and symmetry of the lower extremity

• Foot type

• Gait

• Heel-and-toe walking

• "Duck" walk

Sitting Position

• Palpation:

o Medial joint line

o Lateral joint line

o Patellar tendon

o Tibial tubercle

o Proximal tibia (pes anserine bursa, Gerdy's tubercle)

• Sulcus-tubercle angle (Q angle at 90°)

Supine Position with Knees Extended

• Palpation: o Warmth

o Swelling

o Patellar facets

o Quadriceps tendon

o Lateral collateral ligament in figure-of-four position

• Active and passive flexion and extension

• Patellofemoral and tibiofemoral crepitus

• Sag sign

• Godfrey's sign

• Quadriceps active test

• Anterior and posterior drawer tests

• Lachman's test

• Varus-valgus stress test

• O'Donoghue-McMurray test

• Medial and lateral pivot shift tests

• Reverse pivot shift test

• External rotation recurvatum test

• Quadriceps atrophy

• Hamstring and calf tightness

Side Lying Position

• Ober's test

Prone Position

• Heel height difference (flexion contracture)

• Apley's compression/distraction test

• External rotation of the tibia at 30° and 90° flexion

• Reverse Lachman's test

• Quadriceps flexibility

From Zachazewski JE, Magee OJ, Quillen WS, editors: Athletic injuries and rehabilitation, p 639, Philadelphia, 1 996, WB Saunders.

along the ligament or at its insertion, and the joint space opening is within 2 mm of the contralateral side, with a firm end point. In a grade II injury, the end point is rela­tively firm and the joint space opens 3 to 5 mm more than the contralateral side in 20° flexion and less than 2 mm more than the normal knee in full extension. A grade I I I

injury or complete disruption of the MCL and associated structures is indicated by a soft end point, and the joint space opens more than 5 mm more than that of the normal knee in 20° flexion and full extension.

Lateral Collateral Ligament Adduction (Varus Stress) Test. The varus stress test

assesses the integrity of the LCL, and thus lateral instability, in one plane. With the patient supine and the leg held in slight external rotation, a gap opens in the lateral joint line when a varus stress is applied to the knee ( Figure 1 6- 1 4) .

External rotation of the leg uncoils the cruciate ligaments, requiring the collateral ligament to resist this stress. The examiner's hand is held on the medial joint l ine to feel for opening of the lateral joint line when varus stress is applied from the medial aspect of the knee . The knee is tested first in full extension and again in 30° knee flexion . It is imper­ative to examine both knees, because some ligamentous lax­ity may be normal in some individuals.

The severity of injury to the LCL and associated struc­tures can be determined by the amount of lateral joint line opening in extension and slight flexion. With the knee in full extension, capsular and other secondary restraints (e .g. , the biceps femoris and popliteus) resist varus stress, even when the LCL is disrupted . Flexion helps relax the secondary restraints for primary testing of the LCL.46

I f excessive lateral joint line opening is seen in full exten­sion, a more severe injury to the secondary structures must be assumed . Lateral joint space opening with the knee in full extension i ndicates some degree of injury to the LCL, posterolateral capsule, arcuate-popliteus complex, iliotibial band, biceps femoris tendon, ACL, PCL, and lateral head of the gastrocnemius. With this more severe injury, the results of one or more rotatory instability tests are also positive.

Grading of these injuries is the same as for MCL injuries and is based on the degree of opening of the lateral joint l ine.

Palpation of the LCL. With the patient supine, the hip is flexed to approximately 70°, abducted maximal ly, and externally rotated with the knee flexed 70° to 90° so that the ipsilateral foot rests on the patient's contralateral leg ( i .e . , figure-of-four position) . As the knee is allowed to relax passively, the examiner palpates the LCL from the fibular head to the femoral condyle. A firm, taut band ( i .e . , the LCL) should be easily palpated . If the patient's knee is not relaxed, the examiner may be fooled by the insertion of the biceps femoris. Both knees should be exam­ined to compare the intact LCL with the injured one.

Anterior Cruciate Ligament Lachman's Test. Outside of the operating room,

Lachman's test is the most sensitive clinical test for deter­mining disruption of the ACL, particularly the posterolat­eral band.47.49 Lachman's test isolates the ACL, which

542 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

Figure 16-13 Valgus stress test in 30° flexion. A gap opens in the medial joint line when a valgus stress is applied across the knee. At 30° flexion, this test assesses the integrity of the medial collateral ligament. (From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic injuries and rehabilitation, p 640, Philadelphia, 1 996, WE Saunders . )

Figure 16-14 Varus stress test in 30° flexion. A gap opens in the lateral joint line when a varus stress is applied to the

knee; this indicates injury to the lateral collateral ligament. ( From Zachazewski JE, Magee DJ, Quillen WS, editors: Athletic injuries and rehabilitation, p 641 , Philadelphia, 1 996, WE Saunders . )

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 543

Figure 16-15 Lachman's test. This test is performed with the knee in 20° to 30° flexion. The examiner stabilizes the distal femur with one hand while pulling the proximal tibia anteriorly with the other hand. (From Zachazewski JE, Magee DJ, Quillen WS, editors: Athletic injuries and

"ehabilitation, p 642, Philadelphia, 1 996, WB Saunders . )

acts as the primary restrallllllg force preventing anterior translation of the tibia relative to the femur. The test is per­formed by stabilizing the distal femur with one hand while moving the proximal tibia forward with the other hand (Figure 1 6- 1 5 ) . The leg is held in 20° to 30° flexion, effec­tively relaxing the secondary constraints of anterior transla­tion. The amount of anterior u·anslation and the quality of the end point indicate potential injury to the ACL.

The grade oflaxity is measured in comparison to the nor­mal contralateral knee, not as the degree of absolute transla­tion. Anterior tibial translation is measured in millimeters. The end point is graded as firm ( normal ), marginal, or soft. If the end point and translation are normal, the Lachman's test result is negative. If the end point is soft and/or if ante­rior translation is increased, the test result is positive. The degrees of anterior translation can be affected by several other factors. A large effusion or displaced meniscal tear can diminish the degree of translation. Muscular guarding and the position of the foot can also affect the side-to-side difference. With an incompetent PCL, the tibia sags posteri­orly at rest, giving a false sense of increased anterior transla­tion. Also, a false negative result on Lachman's test can occur if the ACL scars to the PCL to the roof of the intercon­dylar notch. A pseudo-endpoint is detected in these cases.

Anterior Drawer Test. This test determines antero­posterior uniplanar instability ( Figure 1 6- 1 6) . With the patient supine, the ipsilateral hip is flexed to 45° and the knee is flexed to 90°. In this position, the ACL is nearly parallel to the tibial plateau. The examiner sits on the patient's forefoot to stabilize the leg. The examiner then grasps the back of the proximal tibia with the index fingers and palpates the hamstring muscles to ensure that they are relaxed . The examiner's thumbs are placed on the anterior medial and anterior lateral joint line to palpate anterior translation as the tibia is drawn forward on the femur. A stepoff at the medial tibial plateau should be palpated

Figure 16-16 Anterior drawer test. This test is performed with the knee in 90° flexion, with the examiner sitting on the patient's foot. The examiner palpates the hamstring tendons to make sure they are relaxed. The thumbs should be placed in the joint line medially and laterally to palpate anterior translation of the tibia during the test. (From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic injuries and

rehabilitation, p 642, Philadelphia, 1 996, WE Saunders . )

to ensure the proper starting position. The knee i s tested with the foot in three positions: neutral rotation, external rotation, and then internal rotation . The amount of transla­tion and the end point are compared with those in the con­tralateral (normal) knee . If excessive anterior translation is evident, the ACL (primarily the anteromedial bundle ), posterolateral capsule, posteromedial capsule, deep MCL, iliotibial band, posterior oblique ligament, and arcuate­popliteus complex may be injured.

Truly isolated acute ACL tears often produce only mini­mally increased anterior translation when the secondary sta­bilizers of the knee are intact, including the posterior capsule and posteromedial and posterolateral capsular structures. For this reason, the anterior drawer test is not as sensitive as Lachman's test for ACL injury. False negative results also can occur with a displaced ("bucket handle" ) meniscal tear, hamstring spasm, and hemarthrosis.

Pivot Shift Test. This test is used to test for injury to the ACL and to assess anterolateral rotatory instability of the knee. 50-52 During this test, the tibia subluxes antero­laterally on the femur. 52 This recreates the anterior subluxa­tion-reduction phenomenon that occurs during functional activities when the ACL is torn. During the test, subluxation occurs in extension and reduction occurs between 20° and 40° flexion; as a result, the patient feels the sensation ofinsta­bility that occurs when the knee buckles ( Figure 1 6- 1 7 ) . The pivot shift result is graded as grade 0 ( normal ) if no shift is present; grade 1 if there is a smooth glide; and grade 2 if the tibia "jumps" back into the reduced position . A grade 3 pivot is marked by transient locking of the tibia in the subluxed position before reduction. 53

A positive pivot shift test is pathognomonic for ACL deficiency. Unfortunately, the sensitivity of the test is affected by guarding and muscular splinting. The sensitivity improves dramatically if the test is done with the patient

544 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

( Figure 16-17 Lateral pivot shift test. This test is performed with the patient supine. The examiner places the heel of one hand behind the head of the fibula and the other hand on the foot. Internal rotation and valgus force of the lower leg are produced with the knee in full extension to sublux the lateral tibial plateau anteriorly. The knee then is flexed to 20° to 30° , which results in reduction of the lateral tibial plateau. ( From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic

injuries and rehabilitation, p 643, Philadelphia, WB Saunders, 1 996. )

under anesthesia.54 Varying the position of the hip ( abduc­tion and slight flexion) and external rotation of the tibia can enhance the pivot shift . 50

The pivot shift test can differentiate partial tears of the ACL from complete injuries. Partial tears produce increased anterior translation, as documented by Lachman's test or instrumented laxity testing, but they produce a negative pivot shift test result under anesthesia. A tear is considered complete if rotational instability is demonstrated by a posi­tive pivot shift test result. For this reason, the pivot shift test can be considered the most important assessment in the evaluation of an ACL injury.

Posterior Cruciate Ligament and Posterolateral Corner

Stepoff Test. This is a sensitive uniplanar test for deter­mining posterior cmciate injury and posterior instability. Nor­mally, the medial tibial plateau protrudes anteriorly 1 cm beyond the medial femoral condyle when the knee is flexed to 90° ( Figure 16-18, A) .55 This stepoff is lost when there is a postelior sag of the tibia associated with injury to the PCL and other secondary restraints to posterior translation of the tibia ( Figure 16-18, B) . The patient is examined in the supine position with the knee flexed to 90°. The examiner places the hands on either side of the proximal tibia at the joint line and palpates the hanlstrings with the fingers to ensure that they are relaxed. The medial tibial plateau, which is easier to palpate than the lateral plateau, is felt in relation to the femoral condyle with the examiner's thumb. A 0.5-cm ( 114 inch) differ­ence in the stepoff between the involved and the uninjured knee is considered a grade I laxity; a l -cm ( 1/2 inch) difference, in which the tibia and femoral condyles are flush, is considered a grade II laxity. If the anterior tibia lies posterior to the femo­ral condyle, indicating a difference of more than 1 cm ( 112 inch) between the involved and the noninvolved knee, a grade I I I laxity i s present.56,57

A

Figure 16-1 8 Stepoff test. A, Normal relationship of the tibiofemoral joint. The medial tibial plateau protrudes anteriorly approximately 1 em (0.5 inch) beyond the medial femoral condyle. B, With injury to the posterior cruciate ligament, the stcpoff is lost. The medial tibial plateau now lies eid1er in line wid1 or posterior to the medial femoral condyle. (From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic

injuries and rehabilitation, p 645, Philadelphia, 1 996, WB Saunders . )

Posterior Sag Test. This is a uniplanar, passive test of PCL function and posterior instabil ity. With the patient supine, the hip is flexed to 45°, and the knee is flexed to 90°. The examiner then views the knee from the lateral side; with a PCL-deficient knee, a loss of tibial tubercle promi­nence will be seen ( Figure 16-19). If the PCL is torn, gravi­tational forces cause the tibia to fall back or sag on the femur. The posterior tibial displacement is more noticeable when the knee is flexed 90° to 110° than when the knee is only slightly flexed. This test is less obvious when significant swelling of the knee is present. The examiner must be aware of tibial tubercle enlargement ( as a result ofOsgood-Schlat­ter disease ) or tibial plateau osteophytes, which can give a false negative result. Different degrees of posterior sag repre­sent varying degrees of injury to tlle PCL, arcuate-popliteus complex, posterior oblique ligament, and ACL. The quadri­ceps active drawer test58 and Godfrey'S sign (Figure 16-20) also can be used to test the PCL.

Posterior Drawer Test. An isolated tear of the PCL leads to increased posterior translation of the tibia that increases with knee flexion. The most accurate means of

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 545

Figure 16-19 Posterior sag test. When a posterior cruciate ligament�cficient knee at 90° flexion is viewed from the side, loss of prominence of the tibial tubercle can be seen. (From Zachazewski JE, Magee DJ, Quillen WS, editors: Athletic injuries and rehabilitation, p 645, Philadelphia, 1 996, WE Saunders . )

Figure 16-20 Godfrey's test. This posterior sag test is performed with the patient's hips and knees flexed to 90° . Disruption of the posterior cruciate ligament results in loss of prominence of the tibial tubercle. (From Zachazewski JE, Magee DJ, Quillen WS, editors: A thletic injuries and

rehabilitation, p 645, Philadelphia, 1 996, WE Saunders . )

diagnosing this injury is the posterior drawer test with the

knee flexed at 90° .59,60 The examiner's thumbs are placed

on the anterior joint line to feel posterior translation as

the tibia is drawn backward on the femur. The medial tibial

plateau should be palpated as a 1 cm (Il2 inch) anterior

stepoff from the medial femoral condyle to ensure the

proper starting position. The knee is tested with the foot

Figure 16-21 Posterior drawer test. The posterior drawer test is performed with the knee in 90° flexion. The examiner palpates the hamstrings posteriorly to make sure they are relaxed. The thumbs are placed in the anterior joint line to palpate posterior translation of the tibia when a posterior force is applied. ( From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic injuries and rehabilitation, p 646, Philadelphia, 1 996, WE Saunders . )

in three positions: neutral position, external rotation, and

then internal rotation. The amount of translation and the

end point are again compared with those in the contralateral

(normal) knee. If excessive posterior translation is evident,

the PCL (primarily the anterolateral bundle ) , arcuate­

popliteus complex, posterior oblique ligament, and ACL may be injured (Figure 1 6-2 1 ) .

Truly isolated acute PCL tears often produce only mini­

mally increased posterior translation when the secondary

restraints of the knee are intact, particularly the posterior

capsule and posteromedial and posterolateral structures.

Some studies have suggested that the meniscofemoral liga­

ments are strong and may act as secondary stabilizers to PCL function. A posterior drawer test with the leg in inter­

nal rotation is reduced if the posterolateral structures or, as

some investigators have suggested, the meniscofemoral

ligaments, are intact.6 l Some investigators believe that a

posterior drawer cannot occur with an intact arcuate-popli­

teus complex, although laboratory studies have revealed that a posterior drawer of no greater than 1 0 mm ( Il2 inch ),

as compared to the contralateral side, can occur with an

isolated PCL injury. False negative results can occur Witll

a displaced bucket handle meniscal tear, hamstring or quad­

riceps spasm, and hemarthrosis.

Grading of this test also requires comparison of the

injured knee witll tlle normal knee. A grade I injury is

one in which the injured to noninjured side-to-side differ­

ence in posterior translation is less than 5 mm ( 1.4 inch),

which usually corresponds to posterior displacement of

tlle tibial plateau to a position that is still anterior to the

femoral condyles. A grade II PCL injury results in 5 to

1 0 mm more posterior tibial displacement on tlle involved

side . Tlus corresponds to posterior translation of the tibial

plateau to the level of tlle femoral condyles. If the tibia

can be posteriorly displaced 10 mm (Il2 inch) or more on

546 CHAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

the involved side compared to the noninvolved side, or poste­rior to the femoral condyles, a grade I I I injury is present.56,57

Although it is important also to assess the end point of the pos­terior drawer test, the end point may return to a normal, firm feel in chronically PCL-deficient knees. Thus the quality of the end point is not as sensitive as with Lachman's test.

Hughston'S Posteromedial and Posterolateral Drawer Signs. Although an isolated injury to the PCL has little effect on tibial rotational laxity or varus or valgus angulation, concomitant injury to the secondary extra­articular restraints results in some aspects of rotatory insta­bility. Posteromedial and posterolateral drawer tests assess rotatory instability combined with PCL injury and are anal­ogous to the Slocum test for rotatory instability associated with ACL injury.62 With the patient positioned as for the posterior drawer test, the foot is internally rotated 30°. Posteromedial rotatory instability is present if most of the posterior translation occurs on the medial side of the knee and/or if the amount of posterior translation increases or does not change. Posteromedial rotatory instability is a result of varying degrees of injury to the PCL, posterior oblique ligament, MCL ( deep and superficial) , semimem­branosus Illuscle, posteromedial capsule, and ACL (poster­omedial corner) .

Next, the patient's foot is placed in 15° external rotation as the examiner sits on the patient's forefoot. If most of the

Figure 16-22

posterior translation occurs on the lateral side of the knee and/or if the amount of posterior translation increases or does not change, posterolateral rotatory instability is pres­ent, indicating an injury to the PCL, arcuate-popliteus complex, LCL, biceps femoris tendon, posterolateral cap­sule, and ACL ( i .e . , posterolateral corner) . Over-rotating the foot can lead to a false negative test, because this can tighten other secondary and tertiary restraints.

Reverse (Jakob ) Pivot Shift Test. This is the most sensitive test for posterolateral rotatory instability and is analogous to the pivot shift for ACL deficiency.53,63 Unfor­tunately, the test is not pathognomonic for PCL injury, because up to 35% of normal knees may have a positive reverse pivot test result.64 During this test ( Figure 16-22), the posterolateral tibial plateau subluxes laterally and posteri­orly on the femur. The knee starts in the subluxed position; the clunk associated with the test indicates reduction. The external rotation recurvatum test62 (Figure 1 6-23) and the tibial external rotation (dial) test 46 ( Figure 16-24) also test for posterolateral rotatory instability.

Posteromedial Pivot Shift Test. A positive result on this test indicates injury to the PCL, MCL, and posterior oblique ligament.65 All three structures must be injured for a positive test result. The patient is positioned supine, and the knee is flexed to greater than 45° while a varus stress is applied, combined with axial compression and

Reverse pivot shift test. A, The knee is flexed to 70° to 80°. The examiner uses the proximal hand to externally rotate the lower leg to sublux the lateral tibial plateau posteriorly. B, A valgus force is applied as the knee is passively extended. C, The lateral tibial plateau reduces as the knee approaches 20° flexion. (From Zachazewski JE, Magee OJ, Quillen WS, editors: Athletic injuries and rehabilitation, p 647, Philadelphia, 1 996, WB Saunders . )

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 547

Figure 16-23 External rotation recurvatllm test, To perform this test, the examiner grasps the individual's big toes and lifts the leg, allowing both knees to go into passive hyperextension, The test result is positive if the affected knee hyperextcnds to a greater degree than the noninvolved knee and appears to be in valgus alignment, Also, the tibial tuberosity is displaced laterally as the lateral tibial plateau subluxes posteriorly, (From Zachazewski JE, Magee DJ, Quillen WS, editors: Athletic

injuries and rehabilitation, p 648, Philadelphia, 1 996, WB Saunders , )

A

B Figure 16-24 Tibial external rotation (dial ) test. A, External rotation is assessed with the knee at 90° flexion, B, External rotation is assessed with the knee at 30° flexion , (From Zachazewski JE, Magee DJ, Quillen WS, ed;tors: Athletic injuries and rehabilitation, p 648, Philadelphia, 1 996, WE Saunders , )

internal rotation, With a posltJve test result, this action causes the medial tibial plateau to sublux posterior to the medial femoral condyle, As the knee is brought into exten­sion, the tibia reduces at approximately 200 to 400 knee flexion, Occasionally the femur appears to rotate internally suddenly as the knee is extended.

Instrumented Testing of the Knee

Several knee ligament arthrometers are commercially avail­able for clinical use to quantify laxity of the knee. These include the KT1 000 Knee Ligament Arthrometer, men­tioned previously, the Acufex Knee Signature System (Acu­fex Microsurgical, Norwood, MA), the Genucom Knee Analysis System ( FaroMedical, Toronto, Canada), and the Stryker Knee Laxity Tester (Stryker Corp . , Kalamazoo, M I ) , Of these, the KT1 000 arthrometer appears to be the most widely used.

The reliability and validity of these devices have been widely studied.66-77 The Acufex and Genucom arthrom­eters appear to be less reliable than the KT1 000.72,73 The standard deviations of measurements from these devies are higher than the KT1 000. Also, the Genucom tends to pro­duce greater ctifferences in displacement between the right and left knees of normal subjects?5,76 The reliability of the Stryker arthrometer has been questioned by King and Kumar/1 who reported that more than 20% of normal knees showed more than a 2 mm variation between knees when tested by ctifferent examiners on the same day, as well as when tested by the same examiner at a 3-week interval . Boniface et al .70 reported that the Stryker arthrometer is valid for detecting ACL injury. They reported that 89% of subjects with unilateral ACL injury had an increase of 2 mm or more compared to the uninjured side .

Intratester reliability and intertester reliability for the KT1 000 have been reported to be high, both within and between days?7 Wroble et al .73 incticated that the 90% con­fidence limit for right-left difference with the KT1 000 was ± 1 .6 mm when measured at 89 N and ± 1 .5 mm when measured at 1 34 N . A confidence interval of this magni­tude is within acceptable limits for the clinical diagnosis of ACL injuries, In vitro and in vivo studies have shown the KT1 000 to be a valid measure for the detection of ACL

548 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

injury. The correlation between measurements made with the KTI 000 and those made with direct transducer read­ings in cadaveric knees was 0.97.66 The mean anterior dis­placement in ACL-intact cadaveric knees was found to be 5 .8 mm, which increased to 1 2 . 1 mm when the ACL was sectioned . In vivo studies demonstrated that 92% of normal subjects had a side-to-side difference in anterior displace­ment of less than 2 mm, whereas 96% with confirmed uni­lateral disruption of the ACL had a side-to-side difference in anterior displacement greater than 2 mm.66 Stratford et al .67 and Highgenboten et al .68 found that testing with the KTI 000 is more sensitive when performed with a 1 34 N load or with manual maximum force. Highgenboten et al.68 measured the knees of 68 patients with the KTl OOO at 1 5 , 20, and 30 pounds (6 .8 , 9, and 1 3 .6 kg) of force. They found that more patients demonstrated a side-to-side difference greater than 2 mm between the injured and noninjured legs at 30 pounds ( 1 3 .6 kg) of force than at 20 pounds (9 . 1 kg) of force. It should be noted that even at 30 pounds ( 1 3 .6 kg) of force, approxi­mately 20% of patients with an ACL-deficient knee demon­strated a side-to-side difference less than 2 mm.

Based on this research, the KTI 000 appears to be a clin­ically applicable instrument that can be used to assess ante­rior laxity in patients with an ACL-deficient knee . The KT I 000 measures anterior-posterior movement of the tibia relative to the femur. It has both a patellar and a tibial sen­sor pad ( Figure 1 6-2 5 ) . The patellar sensor pad rests on the patella. When the patella is compressed against the femur, the patellar sensor pad indicates the position of the femur. The tibial reference pad rests in the area of the tibial tuber­osity and provides a point of reference for the tibia. Relative motion between the patellar and tibial sensor pads indicates anterior and posterior translation of the tibia on the femur. The KT I 000 also has a force-sensing handle that can be used to provide an anteriorly directed force of 1 5 , 20, and 30 pounds (6 .8, 9, and 1 3 .6 kg), as well as a posteriorly

directed force of 1 5 and 20 pounds (6.8 and 9 . 1 kg) . Tibiofemoral motion is measured in millimeters as the rela­tive motion between the patellar and the tibial sensor pads and is displayed on a dial that can be zeroed to the neutral starting position.

Before using the KTI 000 to assess anterior-posterior laxity of the knee, the clinician must screen for PCL injury. This is done by observing for lack of a stepoff between the medial femoral condyle and the medial tibial plateau. The posterior sag test or the active quadriceps drawer test (or both) also can be done to rule out injury to the PCL. Fail­ure to detect a PCL-deficient knee before testing with the KTI000 may result in a false positive result for anterior lax­ity. With a PCL-deficient knee, gravity causes the tibia to sublux posteriorly. If this goes undetected, the reference position of the tibia is posterior to the true neutral position of the tibiofemoral joint. Performing a KTI 000 test from a starting position at which the tibia is posteriorly subluxed results in a false positive increase in anterior translation . This occurs as the tibia is translated anteriorly from the pos­terior subluxed position to the neutral position. Failure to detect a PCL injury when performing a KTI 000 test inva­lidates the results.

Once PCL injury has been ruled out, the examiner places the patient's knees in 20° to 30° flexion by placing a bolster under the distal aspect of the thighs. The bolster should be placed proximal to the knee to avoid restricting tibial translation . The angle of knee flexion should be recorded so that it can be repeated for future tests. A foot­rest is placed under the patient's feet just distal to the lat­eral malleoli to block external rotation of the leg, which produces relative internal rotation of the tibia in relation to the femur. Accurate placement of the footrest is impor­tant to obtain symmetrical tibiofemoral rotation, which is necessary for an accurate test result (Figure 1 6-26 ) .

The KT1 000 is applied to the lower leg so that the arrow on the arthrometer is aligned with the tibiofemoral

Patellar sensor pad

Figure 16-25 Use of the KT1 000 arthrometer (MEDmetric, San Diego) to quantity tibial translation . Relative movement of the tibiofemoral joint is measured as motion between the patellar and tibial sensor pads. ( From ZachazelVski JE, Magee DJ, Quillen WS, editors: Athletic injltries mid rehabilitation, p 650, Philadelphia, 1 996, WE Saunders . ) - --

- - -

Tibial sensor pad

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 549

Figure 16-26 Position of the lower extremity for the KT1 000 arthrometer test. A bolster is placed under the distal aspect of the thigh to flex the knee to 20°-30°. A foot rest is placed distal to the lateral malleolus to produce symmetrical internal rotation of the tibia on the femur. (From Zachazewski JE, Magee DJ, Quillen WS, editors: Athletic

injuries artd rehabilitation, p 65 1 , Philadelphia, 1 996, WE Saunders . )

joint line. The arthrometer also should be slightly rotated on the leg so that compression of the patellar sensor pad against the patella causes the patella to compress directly against the femur without medial or lateral displacement. The height of tlle patellar reference pad is adjusted so that the needle on the dial faces the 1 2 o'clock position. Once the artllrom­eter has been placed accurately, it is secured to tlle leg with two Velcro straps (Figure 1 6-27) .

The examiner encourages tlle patient to relax by oscillat­ing the tibiofemoral joint. Several posterior pushes are per­formed to establish tlle neutral reference position before

Figure 16-27 Proper alignment of the KTI OOO arthrometer on the lower leg. The arrow on the arthrometer is aligned with the medial joint line, and the arthrometer is slightly rotated onto the leg so that compression of the patellar sensor pad directly compresses the patella against the femur without medial or lateral displacement. The height of the patellar sensor pad is adjusted so that tile needle faces the 1 2 o'clock position on the dial. (Med Metric: KT- J 000 Knee Ligament Arthrometer, Med Metric, San Diego) ( From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic injuries and rehabilitation, p 65 1 , Philadelphia, 1 996, WE Saunders . )

Figure 16-28 Anterior and posterior displacement are measured with the KT1 000 arthrometer. ( Med Metric, San Diego. ) (From Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic injuries and rehabilitation, p 65 1 , Philadelphia, 1 996, W B Saunders . )

the test i s started. Once tlle neutral starting position of the tibiofemoral joint has been determined, tlle dial is rotated so that zero lies under the needle; this indicates the reference-neutral position for tlle test. Once tlle zero reference position has been set, the test is conducted by performing successive anterior pulls and posterior pushes through the force-sensing handle ( Figure 1 6-28 ) . The amount of anterior displacement is recorded with the appli­cation of 1 5 , 20, and 30 pounds (6 .8 , 9, and 1 3 .6 kg) of force, as indicated by the force-sensing handle. Posterior displacement witll the posterior push through the force­sensing handle is measured at 1 5 and 20 pounds (6 .8 and 9 . 1 kg) of force. After each anterior-posterior cycle, the needle on the dial should return to tlle zero reference position . Failure to return to tlle zero reference point may indicate that tlle patient is not fully relaxed or tllat the arthrometer has moved from its initial starting position . Care should be taken when performing the test to avoid rotating or moving the arthrometer in a superior or inferior direction. The anterior drawer test is also performed witll a maximum manual force, which is applied to the poste­rior aspect of the proximal calf. The quadriceps active drawer test is performed by having the patient contract the quadriceps with sufficient force just to raise tlle heel off tlle table. Both the noninvolved and involved knees are tested.

Side-to-side differences are calculated for each level of force by subtracting translation of tlle involved side from the noninvolved side. Positive values indicate increased translation on the involved side . A side-to-side difference in anterior or posterior translation less 2 mm is considered normal. A side-to-side difference of 3 mm or more for anterior translation is considered diagnostic for injury to the ACL (Table 1 6-4) .

550 CHAPTER 1 6 • Knee: ligamentous and Patellar Tendon Injuries

Table 1 6-4

Interpretation of Side-to-Side Differences With the KT1 000 Arthrometer

Test Normal (mm) Equivocal (mm) Diagnostic (mm)

20 Pound (9. 1 kg) anterior drawer <2 2-2.5 :0:: 3 30 Pound ( 1 3 .6 kg) anterior drawer <2 2-2.5 :0:: 3 Maximum manual anterior drawer <2 2-2.5 :0:: 3

From Zachazewski JE, Magee OJ, QuiUen WS, editors: Athletic injuries and rehabilitation, p 652, Philadelphia, WB Saunders, 1 996.

The procedure for the KT 1 000 test must be modified if the patient is suspected of having a torn PCL. In patients suspected of having a PCL injury, the test should be per­formed with the knee in the quadriceps- neutral position. The quadriceps-neutral position is defined as the angle of knee flexion at which contraction of the quadriceps does not result in anterior or posterior translation of the tibia. The quadriceps-neutral position is determined on the non­involved knee by placing the knee in approximately 70° to 90° flexion. The patient then is instructed to contract the quadriceps by sliding the heel along the table while transla­tion of the tibia is palpated. The angle of knee flexion is adjusted until no tibial translation is felt with isolated con­traction of the quadriceps. Once the quadriceps-neutral angle has been determined, it is measured with a standard goniometer. Daniel et al.58 found that the quadriceps-neu­tral angle averages 7 1 0 .

After the quadriceps-neutral angle is found, the KT1 000 arthrometer is placed on the leg so that the arrow on the arthrometer is in line with the tibiofemoral joint l ine. The arthrometer is held in place with Velcro straps. When the arthrometer is secure and in place, the height of the patellar pad is adjusted so that the needle on the dial is directed toward the 1 2 o'clock position. The dial is adjusted to set the zero reference position for the knee. Anterior translation and posterior translation of the tibia are measured with 20 pounds (9 . 1 kg) of force. In addi­tion, the patient is instructed to contract the quadriceps with the KT1 000 in place to determine the active q uadri­ceps drawer displacement. Once measurements are com­pleted on the noninvolved knee, the involved knee is placed at the same angle of knee flexion as the quadri­ceps-neutral angle found on the non involved knee. The KT1 000 arthrometer is applied to the leg, and anterior translation and posterior translation at 20 pounds (9 . 1 kg) of force are measured. The active quadriceps drawer is measured by having the patient contract the quadriceps m uscle.

The active quadriceps drawer measurements are used to calculate corrected anterior and posterior translation for the noninvolved and involved knees. The corrected posterior drawer is calculated by adding the active quadriceps drawer to the measured posterior drawer. The corrected anterior

drawer is calculated by subtracting the active quadriceps drawer from the measured anterior drawer (Figure 1 6-29). Side-to-side differences for corrected anterior and posterior tibial translation are determined by subtracting the values for the involved knee from those for the noninvolved knee. A positive value indicates more translation on the involved side . A non involved to involved difference in corrected pos­terior translation greater than 3 mm indicates injury to the PCL.

Huber et al . 78 found moderate test-retest reliability within and between novice and experienced testers. This was determined on 22 subjects who had a PCL-deficient knee or had undergone PCL reconstruction. Intraclass cor­relation coefficients ( ICCs) for the novice tester were 0 .67 for corrected posterior translation, 0 .59 for corrected ante­rior translation, and 0 .7 for determination of the quadri­ceps-neutral angle. For the experienced tester, ICC values were 0 .79 for corrected posterior translation, 0 .68 for cor­rected anterior translation, and 0 .74 for determination of the quadriceps-neutral angle. Reliability between testers was 0.63 for corrected posterior translation and 0.64 for corrected anterior translation . Standard of error measure­ments were used to construct 95% confidence intervals (CIs) . For the novice tester, the 95% CI for corrected pos­terior translation was ±3.0 mm, whereas for the experi­enced tester it was ± 1 .2 mm. The 95% CI between testers for corrected posterior translation was 2 .0 mm. These results indicate that the KT1 000 can be used with moder­ate reliability to measure anterior and posterior translation in a PCL-deficient knee. Also, the experience of the tester is an important consideration in the interpretation of the test results.

Special Diagnostic Studies

Radiography Radiograp�s of the knee should be obtained after any acute trauma. If the trauma was severe and the patient complains of pain when the knee is moved, radiographs should be obtained before the physical examination is started. Frac­tures must be ruled out before the knee is manipulated, because displacement of the fracture may damage other structures, including neurovascular structures.

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 551

Measured Laxity

20-lb anterior position

Quadriceps active position (QAP)

Knee resting position

(sag position)

20-lb posterior position

Figure 16-29

Corrected Laxity

Corrected anterior

Corrected posterior

Use of quadriccps active drawer mcasurcments to calculate corrected anterior and posterior translation in a posterior cruciate ligament­deficicnt knee. The corrected posterior drawer is calculated by adding the active quadriceps drawer to the measured posterior drawer. The corrected anterior drawer is calculated by subtracting the active quadriceps drawer ITom the measured anterior drawer. (From Daniel OM, Stone ML, Barnett P, Sachs R: Use of the quadriceps active test to diagnose posterior cruciate ligament disruption and measure posterior laxity of the knee, ] Bone Joint Stt'l! Am 70:386-39 1 , 1 988. )

Our standard radiographic series for the knee includes a flexion weight-bearing anteroposterior (AP) and lateral and skyline views. Because ligaments and menisci are radiolucent, radiography is lIsed for the most part to exclude other causes of knee pain, sweLling, deformity, and/or loss of function. Other radiographs obtained in special circumstances that may be beneficial include a long cassette AP weight-bearing view to assess alignment; stress radiographs in cases of sus­pected ligamentous or physical injury; a cross-table lateral view to look for hemarthrosis with a fat-fluid level, an indica­tion of a fracture; and external and internal rotation views to look for loose bodies or oblique fracture lines.

When viewing standard radiographs of the knee, the examiner should look for any obvious intra-articular or osteochondral fractures, calcifications, joint space narrow­ing, epiphyseal damage, osteophytes or lipping, loose bod­ies, tumors, accessory ossification centers, alignment deformity (varus-valgus) , patellar alta or baja, asymmetry of the femoral condyles, and dislocations. Secondary signs can be seen on plain radiographs to help diagnose ligamen­tous or meniscal injury.

Soft tissue swelling as seen on radiographs is helpful when the injured structures are surrounded by fat. An MCL injury may reveal only soft tissue swelling on the medial aspect of the knee. A bloody effusion, often asso­ciated with intra-articular ligament damage, is detected as a soft tissue density in the suprapatellar pouch on the lateral view. Fat in the effusion, or lipohemarthrosis, suggests a fracture (osteochondral or intra-articular) and is identified as a fat-fluid level on a cross-table lateral projection. Although fat globules occasionally are seen in many other types of effusions, the accumulation of fat is much greater in cases of trauma?9 Meniscal tears, although often asso­ciated with effusions, do not produce as large an effusion as a cruciate ligament disruption or intra-articular fracture. Furthermore, the timing of the radiograph in relation to the time of injury is important, because cruciate liganlent injuries are associated with acute effusions, but meniscal tears usually do not produce a significant effusion for at least 1 2 hours.

Although extensive fractures about the knee are readily identified by standard radiographs, careful evaluation of the films may be required to detect avulsion injuries at the attachment sites of ligaments. This is particularly true in children, in whom cruciate l igament injuries frequently involve avulsion fractures. An avulsion of the ACL inser­tion may be seen on the flexion AP radiograph or on the lateral view by identifying the displaced fragment superior and anterior to the tibial spine.80 Segond's fracture, also known as tile lateral capsular sign, is an avulsion fracture of the lateral capsule posterior to Gerdy's tubercle on the proximal lateral tibia.8 1 This fracture, seen on AP radio­graphs, is an indirect sign of ACL injury. The thin frag­ment of bone is vertically oriented and located proximal and anterior to the fibular head and should not to be confused with a lateral ligamentous injury. Avulsion of tile tibial insertion of tile PCL may be seen on lateral radiographs in tile posterior intercondylar area. A PCL avulsion may be a small flake of bone or a large bony frag­ment. Lateral ligamentous injury may be identified on an AP or external rotation view as an avulsion of the biceps femoris or LCL insertion from the fibular head. Uncom­monly, the MCL or LCL may avulse from the femoral con­dyle with a bony fragment. These injuries can be identified on AP radiographs.

Chronic knee injuries may also produce abnormal find­ings on radiographic studies. The lateral notch sign, an

552 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

expansion of the normal indentation of the lateral condyle by 2 mm or more, has been correlated with an ACL-defi­cient knee.82

A chronic MCL injury may result in calcification at the site of injury. When this occurs at the femoral origin of the MCL, it is called Pelligrini-Stieda disease. Although the natural history of isolated cruciate ligament injuries is debated, most authors agree that if left untreated, the lU1stable knee develops degenerative osteoarthritic changes. Osteoarthritic change in the cruciate-deficient knee tends to occur first in the medial compartment, but the compart­ment with meniscal pathology often develops degenerative changes.83 This is best seen on 450 flexion, weight-bearing, posteroanterior ( PA) radiographs.84 Degenerative changes identified on radiographs in a patient with a history of triv­ial trauma with signs of possible meniscal pathology may suggest a degenerative meniscal tear.

Stress radiography has been advocated for knee ligament injuries, but it is difficult to carry out after acute trauma.8S In chronic injury or in the anesthetized patient, these radiographs are more easily obtained and can be valuable. In children with varus or valgus instability, these films can differentiate between ligamentous disruption and a Salter I physeal fracture (fracture through the growth plate with­out displacement) . Stress radiography is particularly popu­lar in Europe to document knee instability in the sagittal and frontal planes;86-90 however, it is not used as often in the United States.

Arthrography Traditional ly, single contrast and double contrast arthro­graphy served as the gold standard for evaluating the menisci and plica and, to a lesser extent, the cruciate liga­ments and articular surfaces? I -97 However, this method is limited in that it is an uncomfortable, invasive procedure that requires a great deal of expertise to perform and inter­pret, and it exposes the patient to irradiation. It was more widely used before the advent of arthroscopy and magnetic resonance imaging (MRI ) . Arthrography has been largely replaced by those two modalities in most centers, but it still may be used in specialized situations to resolve a specific question or when the availability or quality of MRI is limited.

Radionuclide Scintigraphy Radionuclide scintigraphy uses technetium-99 methylene diphosphonate (MDP) to screen for a variety of abnormal­ities. In general, the scintigram reflects the relative blood flow to an area and the degree of bone turnover (osteogen­esis and osteolysis ) . The test is sensitive but nonspecific. It provides more information about osseous physiology than structural characteristics. The technique traditionally has been used to evaluate arthritic joints, stress fractures, tumors, osteonecrosis, infection, osteolysis, metabolic or metastatic bone disease, and reflex sympathetic dystrophy.

Increased osseous metabolic activity, as determined by scin­tigraphy, has also been seen with knee disorders previously considered to involve only soft tissue failure, including symptomatic tears of the ACL.98- 1 04

Diagnostic Ultrasonography Ultrasonography has been used to evaluate various struc­tures of the knee, including the menisci and ligaments. l OS

It is most useful in the evaluation of patellar tendonitis and partial patellar tendon tears. This technique is techni­cian dependent, and although it is inexpensive, it has not been popularized for routine use in the evaluation of liga­mentous and meniscal injuries. It is used in the United States primarily for evaluating patellar tendonitis and masses about the knee.

Computed Tomography Ever since the early application of computed tomography ( CT) to the musculoskeletal system, this technique has been used to evaluate many disorders of the knee. 1 06- 1 08 However, CT scanning is best used for bony detail, because soft tissue detail is better with MlU or arthroscopy. Many conflicting descriptions have been reported with respect to the need for and type of intra-articular contrast material and patient positioning in the CT scanner. Therefore clini­cal use of CT scanning after meniscal and ligamentous injury currently is not widely accepted.

Magnetic Resonance Imaging MRI is a sensitive, noninvasive, noniol1lz1l1g radiation means of evaluating the structural integrity of the knee. It is particularly helpful for visualizing soft tissue structures. At first, MRI met some resistance because initial studies were less accurate than double contrast arthrography, and the procedure was time-consuming and expensive. 1 09- 1 1 2 Improvements in hardware and software, as well as increas­ing expertise in the interpretation of these studies, have overcome these problems, and MRJ has become the pro­cedure of choice for evaluating acute knee injurics l l 3- 1 1 8 Partial and complete tears of ligaments and menisci, as well as otller pathological changes, such as bone bruises and effusions, can be identified with MRJ . Evaluation of the knee by MRJ is reader dependent, but its accuracy approaches 1 00% in diagnosing lesions of tile PCL, ACL, medial meniscus, and lateral meniscus (diagnosis is least accurate with the lateral meniscus ) . 1 1 3, 1 1 6, 1 1 8- 1 2 1 Some clinicians believe this technique is overused, 1 22 and in the future its use may be limited by tile expense. Nonetlleless, M RJ can help diagnose injuries when the patient cannot relax for an adequate examination and can provide addi­tional information about concomitant intra-articular knee 1I1Junes.

Increased signal intensity in the subchondral bone (bone bruises) has been found in specific patterns. Up to 80% of patients with an ACL injury show increased subchondral

Knee: ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 553

signal in the posterior aspect of the lateral tibial plateau and the anterior aspect of the lateral femoral condyle as a result of abnormal impaction of these surfaces secondary to the transient subluxation of the lateral compartment after an ACL injury. 1 23. 1 25 This pattern is distinctly different from bone bruises seen after patellar dislocation and PCL injury. Bone bruises are less common after isolated PCL injuries.

The authors' current indications for an MRI are as follows:

• An acutely injured knee in which an ACL tear is likely but it is unclear whether the patient has associated meniscal or chondral pathology

• Complete evaluation for preoperative planning for a knee with multiple-ligament injuries

• An unclear diagnosis based on the history, physical examination, and standard radiographs

• A patient who cannot relax or cooperate during tile physical examination

• A clinical course not commensurate Witll the clinical diagnosis

• A high ievel athlete with an acute injury who needs an immediate, thorough evaluation to determine the extent of injury and the need for surgical or nonoper­ative treatment

• Evaluation of an occult fracture • Investigation of the cause of poor range of motion

after ligament reconstruction surgery Other uses of M RI include evaluation for soft tissue

masses, tumors, osteonecrosis, osteochondritis dissecans, and extensor mechanism injuries, including tendonitis.

Arthroscopy Arthroscopy currently is the most commonly performed orthopedic procedure in tile United States. It allows for direct visualization of all intra-articular structures, and it can be used to diagnose and surgically treat lesions of the knee. For many acute knee injuries, the best opportunity for complete recovery is Witll prompt, appropriate surgical treatment. The benefit of artllroscopy, tllerefore, is that all patllology can be correctly identified and treated as needed. Arthroscopy uses smaller incisions tlun open surgery, allows better visualization witll less morbidity, and can be performed witllOut tile use of a tourniquet. Partial tears of the ACL sometimes cannot be differentiated from com­plete tears, even with an examination under anesthesia. Using arthroscopy, the surgeon can determine whether the ACL is partially or completely torn. Furthermore, if the ligament is partially torn, the extent of injury can be ascertained to guide treatment. Arthroscopy can also be used to evaluate meniscal patllology and determine whether the lesion should be left alone, repaired, or excised. It also has been shown tllat complete, isolated PCL disruptions may yield a negative posterior drawer sign, even lU1der anesthesia, but tllese can be djagnosed with arthroscopy. 1 26

Altll0ugh invasive, arthroscopy is a relatively low risk procedure; it has a complication rate of less than 1 % and an infection rate of approrimately 0 . 1 %. 1 27, 1 28 Altllough the risk of anestllesia exists, some authors have found local anesthesia to be effective and safe . 1 29. 1 33 This is important, because several investigators are evaluating the efficacy of diagnostic and therapeutic office arthroscopy. Nonetheless, diagnostic artllroscopy has been largely replaced by MIU .

Epidemiology, Biomechanics, and Classification of Knee Ligament Injuries

Straight Plane Versus Rotatory Instabilities

The terminology used to classify knee ligament injuries is tile source of much confusion. This partly arises from tile use of inappropriate terminology to describe and classify movement of the knee. Noyes et al. 1 34 defined terms tllat should be used to describe the motion and position of tile knee. Motion of the knee is accompanied by rotation and translation of the joint surfaces. Translation refers to move­ment that results when all points of an object move along paths parallel to each other. A fixed point on one surface engages successive points on the opposing surface, much like a tire sliding on an ice patch when the brakes are locked. In the knee, translation of the tibia has three inde­pendent components, known as translational degrees of

freedom: medjal- Iateral translation, anterior-posterior trans­lation, and proximal-distal translation . Translation of the tibia is commonly reported in millimeters of motion .

Rotation occurs when successive points on a given surface meet successive points on an adjacent surface. The surface appears to be going in circles about an axis of rotation. Rota­tion of tile joint is simjlar to a tire rolling down a road. In the knee, rotation has tllree independent degrees of freedom . Flerion and extension rotation occurs in the sagittal plane about an axis located through the femur, which lies in the coronal plane. Abduction and adduction rotation occurs in the coronal plane through an aris in the sagittal plane. Inter­nal and external rotation occurs in the transverse plane around a vertical axis, which is located near the PCL. Rota­tion of the knee is measured in degrees of motion.

Motion of the knee involves a complex combination of rotation and translation of tile joint surfaces. According to the convex-concave rule, flerion of the knee is associated witll posterior translation and rotation of tile tibia. When tile tibia is fixed, flerion of tile knee occurs as posterior rota­tion and anterior translation of the femur. Extension of the knee involves anterior rotation and translation of tile tibia. When tile tibia is fixed, extension of tile knee involves ante­rior rotation and posterior translation of the femur. This combination of rotation and translation is necessary to keep the femur centered over tile tibial plateaus throughout the range of motion. As described earlier, rotation and transla­tion of the joint surfaces during movement of tile knee are

554 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

controlled by the geometry of the joint surfaces, tension in the ligamentous structures, and muscular contraction. Dis­ruption of ligamentous or musculotendinous structures alters the normal arthrokinematics of the knee and may lead to progressive degeneration of the joint surfaces.

The terms laxity and instability often are used inter­changeably. The meaning of these terms must be clarified to improve communication among health care professionals in the evaluation and treatment of knee ligament injuries. The term laxity can be used to indicate slackness or lack of tension in a ligament or to describe looseness of a joint. Lax­

ity also is used to indicate the amount of joint motion or play that results with the application offorces and moments. Lax­ity of a joint can be normal or abnormal; therefore the adjec­tive abnormal should be used to indicate laxity that is pathological. In addition, laxity can refer to either transla­tion or rotation, and this should be clearly specified. For example, anterior laxity of the knee can refer either to ante­rior translation or to rotation of the tibia. If anterior laxity

is used to describe translation of the tibia, the more precise ( and preferable) term is anterior translation. The amount of laxity often is recorded as the difference between the involved and noninvolved knees, and this should be clearly indicated. Owing to the ambiguity in the use of the term lax­

ity) Noyes et a ! . 1 34 recommended that it not be used to describe joint motion or displacement. They recommended that the term be used in a more general sense to indicate slackness or lack of tension in a ligament. When referring to motion of the knee, it is preferable to describe the specific motion as translation or rotation.

According to Noyes et al . , 1 35 the term instability can be used to describe the symptom of giving way or the physical sign of increased mobility of the joint. To avoid ambiguity, they recommend avoiding use of the term instability to indicate an episode of giving way. They prefer to use it to indicate a physical sign that is characterized by an increased or excessive displacement of the tibia resulting from trau­matic injury to the stabilizing structures.

Ligamentous injury to the knee results in varying degrees of abnormal laxity or instability, as just described. Hughston et al. 1 36 classified instability that arises as a result of a knee lig­ament injury as straight plane or rotatory instability.

A straight plane instability implies injury that allows for equal translation of the medial and lateral tibial plateaus. According to Hughston et a! . , 1 36 straight plane instabilities include posterior, anterior, medial, and lateral instability. Posterior instability occurs with injury to the PCL com­bined with injury to the arcuate complex and posterior oblique ligament; this results in equal posterior translation of the medial and lateral tibial plateaus when a posterior drawer force is applied. Straight anterior instability occurs with a tear of the ACL and PCL, along with the medial and lateral capsular ligaments. With a straight anterior instability, the two tibial plateaus sublux anteriorly an equal amount when an anterior drawer test is performed. Straight

medial instability occurs with a tear of the medial compart­ment ligaments and the PCL; this results in a positive val­gus stress test with the knee in full extension. Straight lateral instability occurs with a tear of the lateral compart­ment ligaments and the PCL; this results in a positive varus stress test when the knee is in full extension.

Rotatory instabilities involve unequal movement of the medial and lateral tibial plateaus and can include anterome­dial, anterolateral, and posterolateral instabilities. Antero­medial rotatory instability occurs when the medial compartment ligaments, including the posterior oblique ligament, are torn. Anteromedial rotatory instability may be accentuated by a tear of the ACL. With anteromedial rotatory instability, a valgus stress test at 30° flexion is pos­itive. In addition, increased anterior translation of the medial tibial plateau is seen when an anterior drawer test is performed with the tibia externally rotated, and the medial pivot shift test may be positive.

Anterolateral rotatory instability occurs with injury to the middle third of the lateral capsular ligaments and is accentuated by a tear of the ACL. With anterolateral insta­bility, an anterior drawer test results in increased anterior translation of the lateral tibial plateau. The lateral pivot shift test also is positive.

Posterolateral rotatory instability implies greater poste­rior translation of the lateral tibial plateau compared to the medial tibial plateau when a posterior drawer force is applied. Posterolateral instability occurs with a tear of the arcuate complex, which results in a positive varus stress test at 30° flexion . The external rotation recurvatum test also is positive.

Com bined rotatory instabilities, such as allteromedial and anterolateral rotatory instability, also can occur.

Butler et al .8 developed the concept of primary and sec­ondary ligamentous restraints. For each plane "Jf motion of the knee, one ligamentous structure serves as the primary restraint. This structure is responsible for restraining most of the motion in a given direction. For example, the ACL is the primary restraint for anterior translation of tlle tibia, providing approximately 85% of the restraining force.s As the name implies, secondary restraints are structures that take on a secondary role in restraining motion in a particu­lar direction. For example, the secondary restraints for anterior tibial translation are the collateral ligaments, the middle portion of the medial and lateral capsule, and the iliotibial band. These structures are responsible for providing approximately 1 5% of the total restraining force to anterior translation of tlle tibia 8

The amount of ligament laxity or instability after injury to the ligamentous structures of the knee depends on tlle extent of injury and the amount of force applied. Injury to the primary restraint tllat leaves the secondary restraints intact may result in a minimal increase in laxity during man­ual examination of tlle knee. However, if both the primary and secondary restraints are injured or stretched, clinical tests for laxity may demonstrate a large increase in motion

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 555

compared to the non involved side . For example, isolated injury to the ACL may result in only a slight increase in anterior tibial translation if the secondary restraints are intact. Over time, with repeated episodes of giving way, the secondary restraints may stretch out, resLtlting in increased anterior tibial translation . It i s important to note that the secondary stabilizers are not as effective as the pri­mary stabilizers in restraining motion in a particular direc­tion. Therefore, over time, the secondary restraints tend to stretch out gradually when the primary restraint has been lost.

Another important consideration for clinicians in performing and interpreting a clinical laxity test is the amount of force applied to the knee. Forces applied during a clinical laxity test are small, ranging from 9 . 1 to 1 8 . 1 kg (20 to 40 pounds) . This is much less than the forces involved in in vivo activities, which may exceed 45 .4 kg ( 1 00 pounds) with strenuous exercise.8 As a result, clinical laxity tests may not accurately describe the stability of the knee in performing strenuous physical activities. The clini­cal laxity test may demonstrate only a slight degree of increased laxity. When more strenuous activities are per­formed, higher loads are placed on the knee, which may result in greater laxity and in complaints of giving way.

Anterior Cruciate ligament

The ACL is one of the most commonly injured ligaments in the knee. Some studies suggest tllat me ACL is the most commonly injured ligament in the general popula­tion. 1 37- 1 39 Omer investigators, however, believe tllat of all knee ligament injuries, including those that do not result in pathological motion (grade I and grade I I injuries) , the MCL i s tlle most commonly injured ligament. 1 37 The ACL is tlle primary stabilizer for resisting anterior transla­tion of the tibia on the femur and serves to control hyper­extension of the knee. The ACL also serves as a secondary stabilizer to resist internal and external rotation, as well as varus and valgus stress. The ACL can be injured by contact or noncontact mechanisms of injury. Pathomechanics include a valgus force applied to a flexed, laterally rotated knee wim the foot planted, or hyperextension, often com­bined with medial rotation . Less common mechanisms of injury include hyperflexion or a direct valgus force.

Mechanisms of Injury to the Anterior Cruciate Ligament

• Valgus force applied to a flexed, laterally rotated knee with the

foot planted

• Hyperextension (often combined with medial rotation)

• Hyperflexion • Direct valgus force

Daniel et al. 1 40 reported mat me incidence of acute ACL injury among members of a managed health care plan was 3 1 per 1 00,000 members annually. Ninety percent of ACL injuries occurred in patients 1 5 to 45 years of age. Most ACL injuries occur as a result of sports activities, par­ticularly tllose mat place high demands on the knee (e .g . , those involving jumping and hard cutting) . 1 4 1 Skiing may be a particularly high risk activity; tlle incidence of ACL injury among adult skiers is 1 in 2000. 1 42

Mounting evidence indicates mat a narrow intercondylar notch may place a patient at greater risk of injury. LaPrade and Burnett 143 reported a higher incidence of acute ACL injuries in individuals wim a narrow notch widtll index . The notch widm index is me ratio of me width of the ante­rior outlet of me intercondylar notch divided by the total condylar widm at tlle level of me popliteal groove. These researchers' prospective study involved 2 1 3 atll ietes at a Division I university, representing 4 1 5 ACL-intact knees. Intercondylar notch stenosis was found in 40 knees ( i .e . , a notch width index less man 0 .2 ) , and 375 individuals had a normal notch widm index . During tlle 2-year follow-up period, seven ACL injuries occurred, six in knees with a narrow notch and one in a knee wim a normal notch width . Souryal and Freeman 1 44 demonstrated similar results in 902 high school atllietes followed prospectively. The overall rate of ACL injury during the 2-year follow-up was 3%. Atllletes who sustained noncontact ACL tears had a statisti­cally smaller notch widm index. Of me 14 amletes Witll noncontact ACL injuries, 1 0 had a notch width index at least 1 standard deviation (SD) below tlle mean.

Currently, no data support tlle premise mat poor condi­tioning or increased physiological laxity places an individual at greater risk of ACL injury; however, women may be at higher risk for tllis type of injury. Malone 145 reported mat women participating in National Collegiate AtllletiC Associ­ation (NCAA) Division I basketball were eight times more likely man tlleir male counterparts to sustain an ACL injury. Furtller research is needed to identify factors that may place women at higher risk for ACL injury. Females appear to have some unique characteristics that may predis­pose mem to injury, including a wider pelvis, increased genu valgum, altered muscular recruitment patterns, increased laxity, and different biomechanical patterns dur­ing atllletic participation. 145- 1 48

Seventy-five percent of ACL ruptures occur in the midsub­stance, 20% involve me femoral attachment, and 5% involve tlle tibial attaclunent. 149 Associated injuries include meniscal tears in 50% to 70% of acutely injured knees and in up to 90% of chronic, ACL-deficient knees/5, 1 26,1 50 chondral inju­ries in 6% to 20% of ACL-injured knees,45, 1 26 coUateral liga­ment injuries in 40% to 75% of ACL-injured knees, 1 50, 1 5 1

and occasionally capsular injuries and knee dislocations. The patient often reports an audible crack or pop at the

time of initial injury. The patient also notes swelling within the first 2 to 6 hours and inability to continue the activity.

556 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

Classification of ACL injuries is based on the extent of the tear and the resulting instability and is largely a clinical diagnosis. Partial tears have increased anterior translation, as documented by Lachman's test or instrumented laxity testing, but they have a negative pivot shift test under anes­thesia. If loss of Ligament function and rotational instability are demonstrated by a positive pivot shift test, the ACL tear is considered complete. Although this determination often can be made in the clinic or by MRl alone, an examination under anesthesia may be required to establish a definitive diagnosis.

The natural history of an ACL-deficient knee is still unclear. A torn ACL does not hea1. 1 52, 1 53 ACL deficiency leads to rotatory instability in many patients and results i n functional disability. This can occur with activities o f daily living in some, with sports activities such as running (decel­eration ) , cutting, and jumping in others, and with no func­tional instability in still another undetermined group. Repetitive episodes of instability may result in meniscal tears, which can result in arthritis. Debate exists as to whether isolated ACL tears, without meniscal pathology, result in degenerative changes within the knee joint. 5 1 , 1 38, 1 40, 1 50,1 52, 1 54, 1 55 ACL-deficient patients who undergo meniscectomy without ACL reconstruction develop degenerative changes more quickly; this is more apparent in patients with higher activity IevelS. 1 56 A direct relationship exists between giving way ( instability) and the activity level, but many patients with an ACL-deficient knee can return to sports at a less stressful level of activity. Fur­thermore, functional instability may also be related to meniscal pathology. As is discussed later in the chapter, meniscal injury directly relates to tlle level of disability, pain, and swelling and the frequency of reinjury.

Posterior Cruciate Ligament

Although tlle true incidence of PCL i njuries is unknown, they are thought to account for 3% to 40% of all knee inju­ries. 1 37, 1 57. 1 59 PCL injury may be more common than rea­lized. PCL injuries are easily missed, because physicians are less familiar Witll tlle clinical examination findings . I nj uries often go undiagnosed and manifest later as instability or pall1.

The PCL is tlle strongest ligament in the knee, 1 60 and a significant force is required to rupture it. Most PCL injuries occur as a result of atllietic, motor vehicle, or industrial accidents. The mechanism of most atllletic PCL injuries is a fall on tlle flexed knee with the foot and ankle plantar­flexed .6 1 , 1 6 1 This imparts a posteriorly directed force on tlle proximal tibia, which ruptures tlle taut ligament that is parallel to tlle force vector, usually resulting in an isolated PCL injury. 1 62 Similarly, in a motor vehicle accident, the knee is flexed and the tibia is forced posteriorly on impact witll the dashboard. Another mechanism of injury to the PCL is a downwardly directed force applied to the migh

while the knee is hyperflexed, such as when landing from a jump S5 Hyperflexion of tlle knee without a direct blow to the tibia can also result in an isolated PCL injury. 1 63

Mechanisms of Injury to the Posterior Cruciate Ligament

• Fall on a flexed knee with the ankle plantar flexed

• Dashboard injury

• Downward force to the thigh while the knee is hyperflexed

• Hyperflexion

Other mechanisms can result in injury to the PCL, but these usually also involve injury to otller ligaments. Forced hyperextension does not usually result in injury to the PCL. 1 64 Rather, hyperextension is more likely to lead to injury to me posterior knee capsule, popliteal vessel, or ACL. 1 57 A posteriorly directed force applied to the antero­medial tibia with me knee in hyperextension may also cause injury to the posterolateral corner1 57 and results in lateral and posterolateral instability. Significant varus or valgus stress injures tlle PCL only after rupture of the appropriate collateral ligament. Therefore, when the PCL is torn, the integrity of tlle rest of the knee must be carefully evaluated.

Seventy percent of PCL disruptions occur on the tibial side, with or witllOut an associated bony fragment, 1 5% occur on the femoral side, and 1 5% involve midsubstance tears. 1 49 Associated injuries with acute "isolated" PCL tears include chondral defects in 12% and meniscal tears in 27%, which occur more commonly in the lateral com part­ment. 1 65 As with chronic ACL tears, me incidence of meniscal and chondral lesions is higher in chronic PCL­deficient knees, 1 65 although in contrast to acute injuries, these more commonly involve the medial compartment.

The patient often reports an audible crack or pop at the time of tlle initial injury. The patient also notes mild to moderate swelling within the first 2 to 6 hours; however, unlike wim ACL injuries, tllese individuals may return to activity, and the injury often is thought to be a minor event. Patients frequently complain of an unstable gait, but pain with weight bearing or anterior knee pain is common. Pain in patients with a chronic PCL-deficient knee also may be partly due to degeneration of the medial or patellofemoral compartments. 1 64 The pain is exacerbated by walking down stairs.

As witll the classification of ACL injuries, grading of PCL injuries depends on the extent of the tear and the degree of resulting laxity. A grade I PCL sprain involves microscoplc partial tearing of tlle ligament, which overall remains intact. The ligament fibers are stretched, causing hemorrhage and microscopic disruption of the ligament. Examination of a grade I PCL injury reveals no increased laxity compared to the contralateral knee, and the end

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 557

point is firm. A grade I I sprain IS also a partial tear, although the injury results in partial loss of function, as determined by a slight increase in posterior translation dur­ing a posterior drawer test; however, a definite end point is noted, and the reverse pivot shift test is negative. This may be a macroscopic or microscopic tear that results in hemor­rhage and stretching of the ligament, but the iigament is stiU in continuity and functions to some degree. A grade I I I sprain of the PCL is a complete tear of the ligament. Loss of ligament function and joint stability are seen; the posterior drawer test result is 2+ to 3+; and the posterior sag test, Godfrey's sign, the quadriceps active drawer test, and the reverse pivot shift test are positive. Posterior tibial translation is excessive, and the end point is soft.

The natural history of the PCL-deficient knee remains controversial. Some patients experience almost no func­tional limitation and compete in high level athletics, whereas others are severely limited during activities of daily living 16 1 , 1 63)66, 1 67 Parolie and Bergfeld I6I suggested that, if adequate quadriceps strength can be obtained, most patients do well with non operative treatment. Dejour et aL 1 68 suggested that patients are symptomatic for the first 1 2 months, during which time they learn to adapt to the PCL injury. After this time, patients do weU, and a high percentage return to sports. They also reported the devel­opment of degenerative changes involving the medial and anterior compartment in chronic PCL-deficient knees, 1 68 but this finding has not been reported by others 6 I , 1 61 , I66

More recently, these positive results of non operative treat­ments have been challenged. Clancy et al.6 1 reported degen­erative changes in the medial compartment in 90% of patients at the 4-year follow-up. Dandy and Pusey 169 followed patients for an average of7.2 years. Seventy percent had pain while walking, and 55% had patellofemoral symptoms. No correlation was seen between ligament laxity and functional results. Keller et al . 1 67 reported on a series of 40 patients at the 6-year follow-up. The longer the interval between injury and follow-up, the lower the knee score. The presence of radiographic degenerative changes directly correlated with lower knee scores despite excellent muscular strength.

Similarly, with long-term follow-up ( 1 5 years ), Dejour et al I68 found progressive deterioration of results. Eighty­nine percent of patients with isolated PCL injuries had pain, and 79% of knees had degenerative changes. These researchers described tlle natural history of PCL deficiency as having three phases: functional adaptation, functional tolerance, and osteoarthritic deterioration.

Laboratory studies confirm tlut PCL deficiency results in increased medial compartment and patellofemoral con­tact pressures tlut can result in arthritis of the knee. 1 70 Whetller surgical reconstruction can alter tlle development of long-term degenerative changes is unclear. Furtllermore, in some patients the PCL apparently may heal, altllough in a lengthened position . 1 7 1 This may explain the variable results of long-term studies of tlle PCL-deficient knee.

Medial Collateral ligament

As noted earlier, the MCL is the most commonly injured ligament in the knee. I 37 However, the incidence of grade I I I injuries to the MCL may be lower than tlle incidence of high grade ACL tears. 1 37 The MCL is injured by a valgus stress to tlle knee tllat exceeds tlle strength of the MCL. This most commonly occurs from a blow to the lateral aspect of the knee during a sports event. Uncommonly, a noncontact valgus injury to the knee, such as occurs 111

skiing, can produce an isolated tear of the MCL.

Mechanism of Injury to the Medial Collateral Ligament

• Valgus stress to a weight-bearing knee

MCL injuries most commonly involve the femoral inser­tion site, which accounts for approximately 65% of all MCL sprains. Approximately 25% of MCL sprains involve the tib­ial insertion. The remaining 1 0% of MCL injuries involve a deep portion of the MCL at the level of the joint line . 1 49 Associated tears of the medial meniscus occur in 2% to 4% of grade I and grade I I MCL sprains, but medial meniscal tears generally do not occur with grade I I I MCL sprains . 1 72- I 74 This is most likely because compression of the medial compartment is required to tear the medial meniscus, whereas injury to the MCL requires tension that unloads the medial compartment.

The diagnosis of an MCL i njury can be made from the history and physical examination alone and usually does not require MRI or arthroscopy. However, if the physical examination is difficult to perform or if damage to other intra-articular structures is suspected, an M RI can be helpful for determining the full extent of the injury. The patient often recalls being hit by another athlete while the foot was planted, feeling the impact on the lateral aspect of the knee and pain on the medial aspect of the knee. In rare cases patients may note a pop at the time of injury, but they more commonly state that they felt a tearing or pulling on the medial aspect of tlle knee . Swelling occurs quickly at the site of injury, and ecchymo­sis may develop 1 to 3 days after injury. With a grade I or I I sprain, the patient may be able to continue to play, but with a grade I I I sprain, the patient usually cannot con­tinue to participate in sports. These patients usually walk with a limp and with the knee partially flexed, because extension stretches the ligament and causes further pain . The patient may not have an effusion if the injury i s isolated to the MCL.

Classification of MCL sprains depends on the extent of the tear and tlle degree of laxity that results. A grade I

sprain involves microscopic tearing of the ligament, which

558 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

overall remains intact. The ligament fibers are stretched, causing hemorrhage and microscopic disruption of the ligament. Examination of the MCL by the aforemen­tioned tests reveals no increase in laxity compared to the contralateral knee, and the end point is firm. However, tenderness is present along the ligament. A grade I I sprain of the MCL is also a partial tear, but the i njury results in partial loss of function, as determined by a slight degree of increased joint opening (3 to 5 mm) on a valgus stress test with the knee in 30° flexion; a definite end point is noted . In full extension, the knee joint opens less than 2 mm more than the contralateral knee. A grade II sprain may represent macroscopic or microscopic tearing, result­ing in hemorrhage and stretching of the ligament, but the ligament is still in continuity and functions to some dcgree. An acute grade I I MCL injury is tender to palpa­tion, and the patient notes pain with stress testing. A grade III sprain is a complete tear of the ligament. Loss of ligament function occurs, and a joint space opening of more than 5 mm compared to the noninvolved knee is seen on a valgus stress test in 30° flexion; an opening of more than 3 mm compared to the noninvolved knee occurs in full extension. Also, no definite end point is noted with stress testing. Significant joint opening in full extension indicates medial capsular injury and possibly injury to the cruciate ligaments. The severity of tender­ness does not correlate with the extent of injury. A grade I I I sprain usually hurts less than a grade I I or grade I injury.

The natural history of isolated MCL tears is a process of healing, regardless of the degree of injury. 1 730 1 79 Patients with proximal injuries involving the femoral insertion tend to have a higher incidence of stiffness. Also, proximal MCL injuries heal with less residual laxity compared to injuries involving the tibial side .

lateral Collateral ligament

Isolated injuries to the LCL of the knee are uncommon. I n fact, they tend to b e the least common injury to the knee, causing only 2% of all knee injuries that result in pathologi­cal motion (grade I I I injuries ) . 1 37 The injury usually is the result of a direct varus stress to the knee, generally with the foot planted and the knee in extension. 1 27 I njury to the LCL tends to occur as a result of nonsports, high energy activities, 1 27, 1 37 because a clirect blow to the medial aspect of the knee is an unusual occurrence in sports. Varus stress to the knee may also occur during the stance phase of gait, with sudden imbalance and a shift of the center of gravity away from the side of injury resulting in tension on the lat­eral structures. This mechanism does not require an exter­nal force to the knee . Another cause of a varus stress to the knee is a sideswipe injury, in which one knee has a val­gus stress and the other a varus stress. The varus injury often has a rotational component.

Mechanism of Injury to the Lateral Collateral Ligament

• Varus stress to a weight-bearing, extended knee

Straight varus injuries result in LCL disruptions. These tend to be tears from the fibular head, with or without avulsion in 75% of cases, from the femoral side in 20%, and midsubstance tears in 5%. 149 Associated peroneal nerve injuries are common (up to 24%), because the nerve is teth­ered as it courses around the fibular head. 1 27 These nerve palsies have a poor prognosis for complete recovery. I SO

Patients with injury to the LCL may hear or feel a pop in the knee and have lateral knee pain. An intra-articular effu­sion may represent a capsular injury or an associated menis­cal or chondral lesion. Because the LCL is extra-articular, isolated LCL lesions do not commonly result in an effusion of the knee.

Often LCL injuries occur in association with injury to other ligaments in the knee. A severe varus stress results in an LCL clisruption, followed by disruption of the pos­terolateral capsule and PCL. The posterolateral corner should be assessed with stress tests for increased varus rota­tion and external rotation at 30° and 90° and compared to the opposite knee. l S I

Classification ofLCL sprains depends o n the extent of the tear and the resulting degree of la,xity. A grade I sprain involves microscopic partial tearing of the ligament, but the ligament overall remains intact. The ligament fibers are stretched, causing hemorrhage and microscopic disruption within the ligament. Varus stress testing reveals no increase in laxity compared to the contralateral knee, and the end point is firm; however, tenderness is present along the liga­ment. A grade I I sprain is also a partial tear, but the injury results in partial loss of function, as determined by a slight increase in joint opening with varus stress testing (3-5 mm) compared to the noninvolved knee with the knee in 30° flex­ion; however, a definite end point is noted. In full extension, the knee joint opens less than 2 mm more than the contralat­eral knee. A grade II LCL sprain may represent macroscopic or microscopic tearing, resulting in hemorrhage and stretch­ing ofthe ligament, but the ligament is still in continuity and functions to some degree. A grade II acutely injured LCL is tender to palpation, and the patient notes pain with stress testing. A grade I I I sprain is a complete tear ofthe ligament. Loss of ligament function occurs, and a joint space opening of more than 5 mm compared to the noninvolved knee is seen with varus stress testing in 30° flexion; an opening of 3 mm or rilore than the noninvolved knee is seen in full extension. I n adclition, no definite end point is noted with varus stress testing. Palpation of the ligament in the figure­of-four position reveals absence of tension in the ligament proximal to the fibular head.

Knee: ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 559

The natural history of the untreated, complete LCL dis­ruption has yet to be determined. Only a few studies with limited subjects have involved isolated LCL injuries. DeLee et al . 1 27 suggested that severe, straight lateral instability with more than 10 mm of joint opening compared to the contralateral knee usually implies that the ACL or the PCL (or both ) has been injured. From the few studies that have been reported, truly isolated LCL injuries appear to do well with nonoperative treatment. 1 27, 1 76, 1 79

Dislocations and Multiple-Ligament Knee Injuries

Knee dislocations and other, less severe multiple-ligament injuries account for approximately 20% of all grade I I I liga­ment injuries of the knee. 1 37 This diverse group of injuries has a variable severity and co-morbidity. Other than com­bined ACL-MCL injuries, combined ligament injuries account for fewer than 2% of all knee ligament injuries. 1 37

Frequent combinations of two-ligament injuries include the ACL-MCL (most common ), PCL-MCL, PCL-LCL, ACL-LCL, and ACL-PCL.

To dislocate the knee, at least three ligaments must be torn. 1 82 In most knee dislocations, both cruciate ligaments and one collateral ligament are torn. Fractures occasionally are associated with knee dislocations, but these fracture-dis­locations are considered a different entity from a dislocated knee and involve injury only to the ligaments.

A person may dislocate the knee by simply stepping in a hole and hyperextending the knee ( low energy) . Disloca­tions also can result from a high energy blow to the knee, such as can occur in a motor vehicle accident. Athletes have sustained low energy knee dislocations during collisions in baseball, rugby, football, and soccer.

Neurovascular injury is uncommon with knee injuries that involve only two ligaments. However, an LCL injury combined with a cruciate ligament injury can result i n enough lateral joint opening t o produce injury to the pero­neal nerve.

Although the knee can dislocate in any direction, the most common directions are anterior and posterior. 1 83,1 84 Knee dislocations may involve damage to multiple struc­tures within the knee, including the cruciate and collateral ligaments, capsular structures, menisci, articular surface, tendons, and neurovascular structures. The nerves and blood vessels in the popliteal space of the knee are easily stretched and torn during dislocation of the knee, and neu­rovascular injury must be ruled out in all cases. Associated injuries include vascular damage in 20% to 40% of knee dis­locations and nerve damage in 20% to 30%. Some knee dis­location case series reports had an amputation rate of the involved extremity of up to 49%. 1 83, 185, 186 Posterior knee dislocations are associated with the highest incidence of popliteal artery injury, 1 83 and posterolateral rotatory dislo­cations have the highest incidence of nerve injury. 1 87 Some

evidence suggests that low velocity knee dislocations may uncommonly result in neurovascular injury. 1 88 On the other hand, ultra-low velocity knee dislocations in morbidly obese individuals have a very high rate of vascular injury. 1 89

Evaluation of vascular status should include palpation of pulses and comparison of the ankle-brachial index (ABI ) . This test involves taking the blood pressure a t the ankle and on the arm at rest and is repeated at both sites after 5 minutes of treadmill walking. It is used to predict the severity of peripheral arterial disease ( PAD). If pulses are asymmetrical, or if an abnormal ABI is obtained, an arte­riogram is required. Recent evidence suggests that serial vascular examinations may replace the arteriogram if ankle-brachial indices are normal . 1 90

Osteochondral and meniscal injuries are rare, partiClI­larly with low velocity knee dislocations. This is most likely because a distraction force is required to dislocate the knee, whereas osteochondral and meniscal injuries are caused by compressive forces. 1 88

The patient with a multiple-ligament injury frequently gives a history of severe injury to the knee, although, as noted earlier, the mechanism may be trivial. The patient often hears a pop. Swelling occurs within the first few hours, but it is not always large because of the associated capsular injury and extravasation of the hemarthrosis. The patient may note deformity of the knee if the knee dislo­cated and remains unreduced . The patient complains of instability and inability to continue with sports and activ­ities of daily living.

Tibiofemoral dislocations are classified by the direction in which the tibia translates in relation to the femur. As mentioned, the knee can dislocate in any direction. For example, if the tibia lies anterior to the femur, the injury is an anterior dislocation. Posterior, medial, and lateral dis­locations of the knee also can occur. Rotatory dislocations occur when tl1e knee dislocates in more than one direction; these include anteromedial, anterolateral, posteromedial, and posterolateral dislocations. Unfortunately, knee dislo­cations can reduce spontaneously; therefore this classifica­tion scheme is not useful. Furthermore, the amount of tibial displacement that occurs at the time of injur y cannot be estimated from physical or radiographic findings. It therefore is helpful to describe the dislocated knee by the ligamentous structures that have been disrupted.

The natural history of knee dislocations and multiple­ligament injuries is unknown. This is due to the uncommon nature of these injuries and to the many types of disloca­tions and mechanisms of injury ( low velocity versus high velocity) that can occur. However, vascular injury asso­ciated with knee dislocation, if left untreated or if not repaired within 8 hours of the time of injury, results in an 86% amputation rate. If surgery to correct vascular injury is completed within 6 to 8 hours, the amputation rate is only 1 1 %. 1 88 Associated nerve injuries have a poor progno­sis for recovery, regardless of tl1e treatment. 1 9 1 , I 92

560 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

The development of instability, loss of motion, and arthritis is unclear with nonoperative treatment. The level of function of patients with multiple-ligament injuries is worse than those with an isolated knee ligament injury. Knee dislocations treated with immobilization and aggres­sive rehabilitation have surprisingly good results with regard to stability, absence of pain, and the range of knee fleltion up to 90° . 193 The incidence of arthritis after multi­ple-ligament injuries has yet to be determined, but increased instability would be eltpected to result in a greater degree of arthritic change.

Treatment of Knee Ligament Injuries

Guidelines for Progression of Rehabilitation

Progression of the rehabilitation program after knee liga­ment injury and/or surgery should proceed in a logical sequence. Generally, the phases of this progression overlap. For example, muscle function may be addressed before full range of motion and flexibility have been restored . Progres­sion of the patient through the sequence must be individua­lized and depends on the nature of the injury and/or surgery, principles of tissue healing, individual signs and symptoms, and the response to treatment. Adequate time must be allowed for tissue healing and remodeling. During rehabili­tation, care must be taken to avoid overaggressive treatment, which is indicated by a prolonged increase in pain after treat­ment and/or regression in the patient's progress.

Determinants of Rehabilitation Progression

• Nature of injury

• Nature of surgery

• Tissue healing principles

• Tissue healing timelines

• Patient's signs and symptoms • Patient's response to treatment

The initial phase of the rehabilitation program should promote tissue healing and reduce pain and swelling. During this period, treatments such as cold and compression may be beneficial for decreasing pain and swelling. A balance must be achieved between mobility and immobility. The healing tis­sues must not be overloaded. Overaggressive treatment dur­ing this period can disrupt the healing process, but prolonged immobilization can also have adverse effects. Pro­longed immobilization is associated with decreased bone mass, changes in the articular cartilage, synovial adhesions, and decreased strength and increased stiffness of ligaments and the joint capsule, which lead to joint contracture and loss of motion. Disuse results in atrophy and diminished oxida­tive capacity of muscle. Immobilization appears to affect slow muscle fibers more than fast muscle fibers . 194, 1 95

The time required for soft tissue healing varies. The response of soft tissue to injury is acute inflammation, which typically lasts several days or until the noxious stimu­lus has been neutralized. During this period, applications of cold and compression may be used to limit and control acute inflammation. Inflammation is followed by fibropla­sia, which involves the proliferation of fibroblasts and the formation of collagen fibers and ground substance. Fibro­plasia usually lasts for several weeks and results in the for­mation of granulation tissue, which is fragile, vascularized connective tissue. During this period, protected motion is encouraged, because it stimulates coLlagen formation and alignment. Excessive loading of the healing tissue should be avoided, because it may disrupt the healing tissue and reinitiate the inflammatory process. Over time, granulation tissue matures and remodels and can withstand greater loads. This process is gradual and depends on the stresses imposed on the tissue; stresses should be gradually and pro­gressively increased to allow the tissues to adapt to the functional demands placed on them.

Rehabilitation of the knee should ensure that full motion symmetrical to the uninvolved knee is restored. Loss of motion after knee ligament injury and/or surgery adversely affects function. Loss of extension affects gait and results in patellofemoral symptoms. Loss of flexion interferes with activities such as stair climbing, squatting, and running. In the early phases of rehabilitation, passive, active-assisted, and active range of motion exercises can be used to increase and/or maintain motion of the knee. In the latter stages of rehabilitation, active and passive stretching can be used to restore motion. Stretching should be sustained and should use low force to maximize creep and relaxation of connective tissue to produce permanent elon­gation. Application of heat before and during the stretch and maintaining the stretch during cooling may also help produce permanent elongation. 196 Neurophysiological stretching techniques, such as contract/relax or contract/ relax/contract, can help restore motion if the limitation is due to muscular tightness.

Mobilization of the patella also may be helpful in restor­ing motion. Inferior glide of the patella is necessary for flexion, and superior glide is necessary for normal function­ing of the extensor mechanism. Decreased superior mobil­ity of the patella interferes with the ability of the quadriceps to pull through the knee extensor mechanism and results in the development of a knee extensor lag. Medial glide and lateral tilt of the patella are necessary to stretch the lateral retinacular structures. The force used during patellar mobilization must be appropriate for the degree of inflammation present. Overly aggressive patellar mobilization aggravates pain and swelling, which can con­tribute to loss of motion. Mobilization of the tibiofemoral joint is rarely necessary but can help restore motion if the limitation of motion is due to hypomobility of the tibiofe­moral joint.

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 561

Rehabilitation after knee ligament injury and/or surgery

must restore function of the muscles that cross the knee as

well as the muscles that influence segments proximal and

distal to the knee. After acute knee injury or in the immedi­

ate postoperative period, the emphasis should be on regain ­

ing motor control. Often acute pain and swelling result i n

inhibition of the quadriceps, and a knee extensor lag devel­

ops. During this period, quadricep sets, straight leg raises

(SLlu), co-contraction in weight bearing (CKC) and iso­

metric hamstring exercises can be performed. Facilitation

techniques such as vibration and tapping, as well as biofeed­

back and electrical stimulation, may be helpful in regaining

motor control . Generally, gaining quadriceps control is

more difficult than gaining conu'ol of the hamstrings.

Resistive exercises are initiated when the individual has

regained full active motion of the knee . Initially, resistive

exercises should be performed with light resistance and

high repetitions to improve muscle endurance. This mini­

mizes stress on healing structures about the knee and

improves the aerobic capacity of slow twitch muscle fibers.

OKC exercises can be used to provide isolated exercise for

the hamstrings and quadriceps. Precautions must be taken

to avoid overloading healing tissues and to prevent the

development of patellofemoral symptoms. CKC exercises

can be used to improve muscle function in functional pat­

terns while minimizing patellofemoral stress . CKC exercises

are progressed as tolerated and may include wall slides,

minisquats, step-ups, and leg presses. Cycling is an excel­lent exercise for developing endurance of the lower extrem­

ity musculature while mll111111zl11g stress on the

patellofemoral and tibiofemoral joints. The use of toe clips

and pedaling with one leg can help increase hamstring

activity. Other forms of endurance exercise for the lower

extremities include step machines, cross-country ski

machines, and swimming.

In the later phases of rehabilitation, resistive exercises

can be progressed to high resistance, low repetition exer­

cises to develop muscle strength and power. High resis­

tance, low repetition OKC exercises are used to improve

isolated muscle strength, but care must be taken to avoid

overloading the patellofemoral joint, as described earlier

in this chapter. High resistance, low repetition CKC exer­

cises can be used to improve strength in functional patterns

with less risk of patellofemoral symptoms; however, patello­

femoral mechanisms should always be considered with the

rehabilitation of any knee injury.

Exercises should incorporate both the concentric and

eccentric phases of contraction. Concentric muscle function is necessary to accelerate the body, whereas eccentric mus­

cle function is necessary to decelerate the body. During a

concentric contraction, the muscle shortens as it contracts,

whereas during an eccentric contraction, the muscle elon­

gates as it contracts. The force-velocity relationship is dif­

ferent for concentric and eccentric contractions. During a

concentric contraction, muscle force decreases as the speed

of shortening increases. During an eccentric contraction,

muscle force increases as the speed of lengthening

increases. Eccentric contractions produce higher levels of

force as a result of lengthening of the series elastic compo­

nent and facilitation of the stretch reflex. To ensure full res­

toration of function, rehabilitation should include

concentric and eccenu'ic exercises. Failure to incorporate

eccentric exercise into the rehabilitation program results

in the development of muscle soreness and an increased risk

of reinjury with return to activity.

For athletes who require power to perform their sport,

plyometric exercises should be incorporated into the final

stages of the rehabiEtation program . Plyometric exercises

develop power and speed and incorporate lengthening of

the muscle immecliately before a powerful concentric con­

traction . These exercises include depth drops and jumps

from heights of 1 5 .2 to 4 5 . 7 cm (6 to 1 8 inches ) , bound­

ing, hopping, and ricochets. The plyometric program must

be carefully planned and implemented to avoid injury.

Once the strength and endurance of the lower extremity

musculature have been established, neuromuscular control

must be developed to enhance dynamic stability of the

knee . This requires learning how to recruit muscles with

the proper force, timing, and sequence to prevent abnor­

mal joint motion. I nitially it requires conscious effort, often

with tl1e help of biofeedback. Through practice and repeti­

tion, control of abnormal joint motion becomes automatic

and occurs subconsciously.

Proprioceptive neuromuscular facilitation techniques,

such as rhythmic stabilization and timing for emphasis,

may be helpful for developing dynamic stability. A variety

of functional activities can also be used to develop dynamic

control of abnormal joint motion. These activities generally

are progressed from slow to fast speed, from low to

high force, and from controlled to uncontrolled activities. The emphasis should be on establishing proper move­

ment patterns to enhance dynamic stability of the joint.

EMG biofeedback may be used to ensure that muscles

are being recruited in the proper sequence to maintain

joint stability. Activities for enhancing dynamic stability

progress from walking, jogging-running, acceleration­

deceleration, sprinting, jumping, cutting, pivoting, and

twisting. Research is needed to determine tl1e effectiveness

of tl1ese techniques.

Anterior Cruciate Ligament Injuries

Treatment of ACL injuries must be individualized. It

depends on the extent of pathology and the level of clisabil­

ity experienced by the patient during sports and activities of

daily living. Therefore, decisions regarding tl1e treatment of

the ACL-deficient knee must be made in collaboration with

the patient, physician, physical therapist, and athletic

trainer. The type of treatment depends on many factors,

including age, activity level, occupation, desire to continue

562 CHAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

sports, amount of functional instability, presence of asso­

ciated injuries and arthritic changes, and amount of laxity.

The patient's willingness to modify activity to a level com­

patible widl functional stability is ilie most important factor

governing treatment options.

Most studies of the natural history of conservative treat­

ment of ACL injuries have shown poor results in young

patients. Persistent instability is common. Noyes et al . 1 97

reported a 65% incidence of giving way during activity,

which was associated wiili persistent pain and disability for

several days thereafter. Hawkins et al . 1 98 reported iliat

86% of patients in his case series had similar findings. Fur­

thermore, dle ability to return to strenuous activity is l im­

ited widlout reconstruction ; only 1 4% to 22% of patients

in this younger age group return to dle same level as their

previous activity. 197- 1 99

In older patients, who accept l imitations on ilieir activ­

ities, results generally are better. Ciccotti et al 200 evaluated

a series of patients 40 to 60 years old who were treated con­

servatively for ACL tears. Ninety-seven percent had a grade

2 or grade 3 on Lachman's test, and 83% had a positive

result on dle pivot shift test; the overall satisfaction rate

was 83%.

Even so, wiiliout treatment, ACL insufficiency predis­

poses the patient to injury of oilier knee structures. The

risk for additional lesions of ilie menisci and cartilage

increases with time. 1 52, 1 99,201 -204 Progressive degeneration

of dle knee has been cited, especially when associated widl

meniscal tears. 1 99,205 Osteoariliritic changes have been

noted to occur widl ACL insufficiency in 2 1 % to 1 00% of

patients.

Factors associated wiili a good outcome for nonopera­

tive treatment include intact collateral ligaments, absence

of meniscal injury and/or ariliritis, and participation in

low demand sports that do not require running, j umping,

or cutting. A factor that militates against a surgical

approach is a minimal increase in tibial translation wiili lax­

ity testing.

Surgical reconstruction of ilie ACL-deficient knee

should be considered if instability of a knee prevents ilie

patient from participating in sports and other activities.

It also should be considered if associated collateral ligament

damage or meniscal injury is present or if a large increase in

anterior tibial translation is seen with laxity testing. Surgery

should be considered in most patients who have high

expectations and plan to compete in sports iliat place high

demands on the knee.

Partial tears of ilie ACL involving more than 50% of the

ligament are more likely to progress to complete tears if

treated nonsurgically. 1 34 In general, however, there is little

correlation between ilie percentage of the tear and ilie clin­

ical outcome. 1 34 Also, the extent of tearing may be difficult

to quantify accurately. For iliis reason, ilie distinction

between a partially torn ACL and a complete tear usually

is a clinical one. A positive result on the pivot shift test,

regardless of wheilier dle patient is awake or under anes­

iliesia, defines functional instability and an incompetent

ACL.

ACL tears in skeletally immature individuals are more

common than previously suspected. Initially these patients

usually are treated nonoperatively. If functional instability

persists after rehabilitation, consideration must be given

to reconstruction of the ACL. Skeletal immaturity is no

longer an absolute contraindication to ACL reconstruction,

but ilie patient must be followed closely to ensure that

growtll has not been arrested.

Nonoperative Treatment Nonoperative treatment after injury to the ACL generally

has fallen out of favor, because advances in surgical and

rehabilitative techniques have improved outcomes and

reduced morbidity. Nonetheless, conservative treatment of ACL injuries may be indicated for more sedentary indivi­

duals who have an isolated injury Witllout damage to other

structures and who are willing to modify tlleir lifestyle to

avoid activities tllat cause pain, swelling, and/or episodes

of instability. Nonoperative treatment of ACL injuries does

not mean that ilie injury is ignored. Treatment should

actively involve ilie patient and includes exercise, functional

training, bracing, and patient education.

Treatment after acute injury to the ACL should focus on

resolving inflammation, restoring range of motion, regain­

ing muscle control, and protecting tile knee from furilier

injury. Cold and compression can be used to decrease pain

and swelling. Range of motion exercises should be per­

formed to restore motion, which should improve as pain

and swelling subside. Failure to regain motion, particularly

extension, may indicate a torn meniscus, and further diag­

nostic studies and/or surgery may be indica:ed . Isometric

exercises for ilie quadriceps and hamstrings should be

initiated to regain motor control and minimize atrophy.

Assistive devices should be used for ambulation while tile

knee is still actively inflamed. The use of assistive devices

can be discontinued once the patient has regained full extension wiiliout a quadriceps lag and can walk normally,

without gait deviations.

More aggressive rehabilitation can begin once inflamma­

tion has resolved and full range of motion has been

restored. The emphasis at this time should be on improving

the strength and endurance of tile muscles rhat cross tile

knee. Particular emphasis should be placed on the muscles

that pull the tibia posteriorly ( i . e . , the hamstrings and gas­

trocnemius ) . The normal quadriceps to hamstring ratio at

a slow contractile velocity is approximately 3 :2 . It has been

suggested tlut rehabilitation of an ACL-deficient knee

should strive to develop a hamstring-dominant knee so that

dle quadriceps to hamstring ratio approaches 1 : 1 . This

seems to be a logical goal for rehabilitation of ACL injuries,

but it should not be achieved at the expense of quadriceps

weakness.

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 563

OKC and CKC exercises can be used to improve

so·ength and endurance. OKC exercises can be used to pro­

vide isolated exercise for the hamstrings and quadriceps.

Precautions must be taken to prevent the development of

patellofemoral symptoms with OKC knee extension . Stand­

ing and seated calf raises can be used to deve.lop the gas­

trocnemius and soleus, respectively. CKC exercises can be

used to develop strength and endurance of the muscles of

the lower extremity in functional patterns while minimizing

patellofemoral stress. CKC exercises are progressed as

tolerated .

Once the strength and endurance of the lower extremity

muscles have been established, neuromuscular control must

be developed to enhance dynamic stability of the knee .

Emphasis should be placed on learning to recruit tlle poste­

rior muscles to minimize anterior subluxation of tlle tibia. The patient should be taught to "set" the hamstrings and

gastrocnemius before foot strike.

Sherrington206 proposed co-activation of the antagonist

during contraction of the agonist. Baratta et a1 . 1 7 and

Draganich et al. 1 9 demonstrated co-activation of the ham­

strings during resisted OKC knee extension. Antagonist­

agonist co-activation probably originates from tlle motor

cortex in the phenomenon known as direct common

drive.207 Activation of the muscle spindle can also facilitate

contraction of the antagonist. 13 As tlle knee extends, mus­

cle spindles lying within the hamstrings are activated and

facilitate contraction. Training the hamstrings to stabilize

we knee dynamically should capitalize on the phenomenon

of co-activation .

A functional brace may be helpful as tlle patient returns

to activity. Exactly how knee braces work is unclear, but

many patients report improved function with the use of a

knee brace. Whether functional braces provide a physical

restraint to abnormal joint motion is doubtful . Several

studies208-2 1 0 have indicated wat knee braces may restrain

tibial translation at low force levels but are ineffective at

controlling abnormal joint motion at functional force levels. It has been proposed that knee braces function by

improving proprioception . Lephart et al . 1 4 reported

enhanced awareness of joint movement sense with the

application of a neoprene sleeve. Application of a knee

brace may stimulate cutaneous receptors and enhance pro­

prioception . In addition, knee braces may enhance con­

scious or subconscious awareness of the injury, helping

the individual to protect oneself from further injury.

Anotller important component of non operative man­

agement of ACL injuries is modification of the patient's

lifestyle to avoid activities associated Witll pain, swelling,

and episodes of instability. Repeated episodes of instabil­

ity cause further injury to the joint, including stretching

of secondary restraints and injury to the menisci and

joint surfaces . Recurrent pain and swelling with activity

indicate additional damage to the joint. Activities that are

not tolerated by the joint should be eliminated to prevent

irreversible degenerative changes. Activities tllat place high

stress on tlle ACL-deficient knee include tllose that involve

jumping, landing, cutting, pivoting, and rapid acceleration

or deceleration on tlle involved extremity. Nonoperative

management is likely to fail patients who are unwilling or

unable to modify their lifestyle to avoid activities associated

Witll increased pain, swelling, and instability; therefore

these individuals should consider surgical reconstruction .

Surgical Treatment Surgical trea011ent of a torn ACL includes di rect repair,

repair with augmentation, and reconstruction with auto­

grafts or allografts. Results of direct repair have been

pOOr. 1 5 1 ,2 1 1 ,2 1 2 A few investigators, however, have been

encouraged by repair witll augmentation . 2 1 3 ,2 1 4 From a

historical perspective, reconso'uctions using synthetic liga­

ments led to early failure and the development of wear par­

ticle debris tllat leads to reactive synovitis.2 1 5.2 1 7

Reconstruction has been successful and remains the

treatment of choice.2 1 5-2 1 7 Reconstruction with augmenta­

tion does not appear to improve the results compared to

reconstruction alone .2 1 8-220 In addition, the use of a liga­

ment augmentation device may result in stress yielding of

the graft, which may delay remodeling.

The timing of surgery after acute injury is an important

consideration in minimizing the risk of postoperative loss of

motion. Most authors recommend delaying surgery until inflammation has subsided and range of motion and muscle

function have been restored.22 1 ,222 A decreased incidence

of loss of motion and a faster return of quadriceps strength

were noted when surgery was delayed 3 to 4 weeks after

acute ACL injury.22 1 ,223,224

Currently, ACL reconstruction is most commonly per­

formed using an artllroscopically assisted technique with

the goal of recreating tlle normal anatomy of the ACL.

An arthroscope is inserted into the knee through two or

iliree small portals. A tibial tunnel is drilled with an intra­

articular exit point at the posterior half of the native ACL

insertion. A second tunnel is drilled in the femur at tlle ori­

gin of the native ACL. Position of the femoral tunnel is

often dictated by the tibial tunnel position as the tibial tun­

nel is used to drill tlle femur. An anatomical and isometric

reconstruction of tlle ACL is performed by positioning a

graft within these tunnels .

Multiple surgical variables contribute to the success of

the operation. Tunnel placement, graft type, graft fixation,

tension, rotation, and notch preparation affect the biome­

chanics of the reconstruction . Graft fixation can be per­

formed by multiple techniques. If a patellar tendon graft

is used, fixation usually is achieved witll interference screws

( Figure 1 6-30) . Soft tissue grafts (e .g . , hamstring, tibialis )

can be fixed with an EndoButton, spiked washers, or a spe­

cial interference screw. An adequate "notchplasty" must be

performed to allow enough space for tlle graft so that the

knee can extend fully witllout impingement. This should

564 CHAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

Figure 16-30 Anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft. Interference screw fixation is used to fix the graft within the tunnels. ( From Zachazewski IE, Magee DJ , Quillen WS, editors: Athletic injuries and rehabilitation, p 665, Philadelphia, 1 996, WB Saunders . )

be determined intraoperatively, and the notch should be

enlarged if the graft impinges in the intercondylar area.

ACL reconstruction techniques have evolved with

advances in the biomechanical evaluation of the knee .

Computer-assisted surgery, high resolution MRl, and eval­

uation of in vivo three-dimensional kinematics recently

have provided new insights into functional evaluations of

ACL reconstructions. These analyses have led to an

increased emphasis on optimization of graft placement.

Several surgeons have proposed that the two functional

bundles of the ACL, the anteromedial bundle and the pos­

teromedial bundle, be reconstructed individually.225-227

The clinical importance of this technique has yet to be

determined. Multiple types of grafts have been used to reconstruct

the ACL. Currently the most common sources of autograft

tissue ( i .e . , tissue from the same individual ) are the bone­

patellar tendon-bone ( B PTB )6 1 ,228,229 and hamstring ten­

dons,230-232 but other graft sources have been used with

success.233,234 The use of allograft tissue ( i .e . , tissue from

another human being ) for reconstruction has become more

prominent, especially in older individuals, as a result of

advances in disease screening techniques, increased tissue

availability, and ease of use in surgery.235-237 Differences

in graft tissue strengtll, stiffness, and graft fixation strength

lead to differences in surgical technique and postoperative

rehabilitation.

The ultimate load to failure of various tissues has been

reported by several i nvestigators (Table 1 6- 5 ) . The quadru­

pled hamstring tendon graft is approximately 91 % stronger

than the native ACL and 39% stronger than the patellar

tendon . The patellar tendon graft is approximately 37% stronger tllan the native ACL. Although three of the four

potential grafts listed in Table 1 6- 5 are stronger than native

ACL, graft fixation strength must be factored into the

equation when a rehabilitation program is developed.

Empirically, the healing of bone to bone in the osseous

tunnel would seem to occur more quickly than the healing

of tendon to bone. However, this has not been proved sci­

entifically. Furtllermore, Witll delayed healing of tendon to

bone, aggressive rehabilitation or activities may appear to

cause tile graft to stretch out. Also, the theoretical advan­

tage of a larger, stronger allograft allowing for more aggres­

sive rehabilitation remains lU1proven .

Recently, Brand e t al 242 reported biomechanical data on

various graft fixation techniques for ACL reconstruction .

These authors reported that the tibial fixation strength for

a patellar BPTB graft was highest Witll a 9-mm interference

screw ( load to failure, 678-758 N ) .243 The femoral fixation

of the BPTB graft was optimal with a metal interference

screw (640 N ) .244,245 Fixation strengths also were reported

for soft tissue grafts. Hamstring graft tibial fixation was

greatest with a washer plate (9 .5 N),246 and with an Endo­

Button with #5 suture on the femoral side.247,248 Noyes

et al .249 have estimated the strengtll required for activities

of daily living to be 454 N, based on tile failure strength

of the ACL.

The autll0rs' clinical approach to designing a rehabilita­

tion progranl based on ACL graft selection is to be less

aggressive initially Witll soft tissue grafts, such as the qua­

drupled hamstring grafts.250 This approach is based on

the premise that soft tissue to bone healing takes approxi­

mately 1 2 weeks, whereas bone to bone healing occurs in

approximately 8 weeks in most cases. With our current

operative technique, patients generally return to sports

within 6 to 9 montlls.

Postoperative Management for Reconstruction of the Anterior Cruciate Ligament Rehabilitation after ACL reconstruction must consider ini­

tial graft strength, fixation, and healing and maturation of

the graft. Initial graft strength depends on the quantity

and quality of the material used and has been investigated

by Noyes et al 249 The central and medial tllirds of the

patellar tendon were found to be 1 86% and 1 59% of the

strength of tile native ACL, respectively. Weaker graft mate­

rials include the semitendinosus ( 70%), gracilis (49%), distal

iliotibial track (44%), and fascia lata ( 36%). The use of

Knee: ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 565

Table 16-5

Ultimate Load to Failure and Stiffness of Various Graft

Selections

Ultimate Strength Stiffness to Failure (Newton-

Graft Selection (Newtons) Meters)

Native anterior cruci3te 2 1 60 240 ligament (Woo et a1 .238 )

Patellar tendon ( Race and 2977 455 Amis239 )

Quadrupled hamstring 4 1 40 807 (Hamner et a1 .240)

Quadriceps tendon (Staubli 2 3 5 3 326 et a1 241 )

stronger graft materials with solid fixation, such as that

provided by an interference screw, allows more aggressive

rehabilitation in the immediate postoperative period.

Graft strength is strongest at the time of reconstruction.

Over time, the graft undergoes necrosis and remodeling.

Healing and maturation of autogenous BPTB grafts in

the animal mode125 1 -254 and in humans25 1 ,255 have been

described, as have healing and maturation of allograft

BPTB grafts in animal models255-259 and humans.254 Initi­

ally, the graft is avascular. By 6 weeks, the graft is enveloped

in a synovial sheath. Revascularization begins 8- 1 0 weeks

after surgery and is nearly complete by 1 6 weeks. Histolog­

ically, the graft shows signs of avascular necrosis 6 weeks

after reconstruction . The graft is invaded by mesenchymal

cells 8 to 1 0 weeks after reconstruction. These cells prolif­

erate and form collagen by postoperative week 1 6 . One

year after reconstruction, the graft takes on the appearance

of a ligament, with dense, oriented collagen bundles. Graft

strength decreases during the period of necrosis and then increases as the graft remodels and matures.

Although the graft takes on the appearance of a normal

ligament, it does not function the same as the native ACL.

Evidence suggests that at 6 months after surgery, allografts

demonstrate a greater decrease in their structural properties

from the time of implantation, a slower rate of biological

incorporation, and prolonged presence of an inflammatory

response compared to autografts.259 Although clinical

results have not demonstrated a significant difference

between allograft and autograft reconstruction, rehabilita­

tion after allograft reconstruction may need to be less

aggressive than that following autograft reconstruction. In

spite of the research that has been done, little i s known

about the graft'S ability to withstand loads and strain dur­

ing healing and maturation. Therefore it is difficult to base

rehabilitation after ACL reconstruction strictly on tile time

required for healing and manu-ation of tile graft.

Postoperative rehabilitation after ACL reconstruction

must minimize the adverse effects of immobil ity witllout

overloading healing tissues. As discussed earlier, basic data

are lacking on the strain and loads that the graft can with­

stand during healing and maturation. In addition, studies

on strain and loads imposed on the graft during exercise

and activity are incomplete. For these reasons, current

trends in rehabilitation after ACL reconstruction are based

on clinical experience .

Rehabilitation after ACL reconstruction has undergone

significant changes over the last decade. In the 1 970s and

early 1 980s, rehabilitation after ACL reconstruction was

conservative. Paulos et a1 .260 described a five-phase pro­

gram that imposed time restraints thought to be necessary

for graft healing and controlled forces tl1at may have been

deleterious to the healing process. In tllis program, range

of motion was limited to 30° to 60° in a cast brace, and

the patient was non-weight-bearing on crutches for 6

weeks. Toe touch weight bearing was initiated in week 7 . The patient was allowed gradually to begin partial weight

bearing on crutches at 1 2 weeks and was allowed to be in

full weight bearing without assistive devices by week 1 6 .

Resisted exercises consisted of hamstring and limited arc

quadriceps exercise using light resistance and high repeti­

tions. No mention was made of CKC exercises. Full return

to activity was delayed for 9 to 1 2 months.

An interest has developed in accelerated rehabilitation

after ACL reconstruction, which initially was popularized

by Shelbourne and Nitz.26 1 The essential features of tlleir

program included early emphasis on restoration of full knee

extension symmetrical to the noninvolved side, immediate

full weight bearing, use of C KC exercises to improve lower

extremity muscle function, and return to full sports partici­

pation in 4 to 6 months . These researchers compared the

results in a group of patients who underwent an accelerated

rehabilitation program witll those in a group that under­

went a more traditional rehabilitation program, which

included immobilization in 1 0° flexion, delayed weight

bearing, reliance on OKC exercises to improve quadriceps

and hamstring function, and delayed return to full activity.

The study found that the accelerated rehabilitation pro­

gram resulted in an earlier and more complete return of full

extension and an earlier return to final flexion without any

adverse effect on tile stability of the knee, as indicated by

side-to-side differences in knee laxity scores. In addition,

isokinetic testing of the quadriceps revealed a higher mean

percentage of involved to noninvolved scores fi'om 4 to

1 0 months postoperatively. However, these differences in

isokinetic scores were eliminated 1 year after surgery.

No differences were seen in tile patients' subjective assess­

ment of their knee fWlction. A second surgical procedure to recover loss of extension was required less often in patients

who wlderwent the accelerated program . Based on these

results, the use of an accelerated rehabilitation program

after ACL reconstruction was recommended because it

566 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

resulted in earlier restoration of motion, strength, and

function without compromising stability of the knee.

Loss of motion has been described as the most common

complication after ACL reconstruction . 222,262-266 Sachs

et al 265 reported a 24% incidence of a knee flexion contrac­

tion greater than 5° after ACL reconstruction; this was pos­

itively correlated with quadriceps weakness and

patellofemoral pain . Harner et al .222 reported an 1 1 % inci­

dellCe of loss of motion, which they defined as a knee flex­

ion contracture of 1 0° or more and/or knee flexion less

than 1 25 ° . All patients with loss of motion experienced loss

of extension, and two thirds also had loss of flexion. Factors

significantly related to the development of loss of motion

included reconstruction within 4 weeks of the initial injury,

concomitant knee ligament surgery involving the medial

capSLlle, and gender ( male ) . Patients with loss of motion tended to have had an autograft rather than an allograft

and to be older, but these trends did not reach statistical

significance. Also, patients who developed loss of motion

used a postoperative brace that limited full extension more

often than did patients who had normal motion after sur­

gery. Loss of extension after ACL reconstruction leads to

an abnormal gait, quadriceps weakness, and/or patellofe­

moral pain . Preoperative, intraoperative, and postoperative recommendations to minimize the risk of loss of motion

were provided .

The goal for postoperative management after ACL recon­

struction is to provide a stable knee that allows return to the

highest level of function while minimizing the risk for loss of

motion. To reduce the risk of loss of motion, postoperative

management after ACL reconstruction should emphasize

control of inflammation, restoration of full extension sym­

metrical to the noninvolved knee, early range of motion

and quadriceps exercises, and restoration of normal gait.

The authors currently use two rehabilitation programs for

patients Witll an isolated ACL reconstruction.250 An acceler­

ated rehabilitation approach is used for young, atllletic

patients, and a slower program is used for older patients whose

needs are more recreational . The main difference between tile

two programs is the rate of progression through the various

phases of rehabilitation and the period of time required for

rehabilitation before running and sports can be resumed .

The authors' accelerated rehabilitation program is

organized into six phases. Certain criteria must be met

before the patient can progress to the next phase. ACL

rehabilitation begins preoperatively, immediately after the

injury occurs. The goals during this phase are to reduce

pain, inflammation, and swelling, restore normal range of

motion ( ROM), and prevent m uscle atrophy. Emphasis is

placed on achieving full passive knee extension to minimize

postoperative complications and arthrofibrosis.26 !

Another critical aspect of the rehabilitation program is

re-establishing voluntary muscle activation of the quadri­

ceps muscle . After damage to the ACL, a protective mech­

anism of quadriceps reflex inhibition and hamstring

facilitation has been observed.267,268 The patient therefore

is instructed to recruit as much quadriceps firing as possi­

ble. This is facilitated through the use of electrical muscle

stimulators or biofeedback units to achieve greater quadri­

ceps muscle activation.

Patient education is another valuable component of pre­

operative rehabilitation. The surgical procedure and tile

postoperative rehabilitation program are explained to the

patient as part of tile mental preparation. During this

phase, an appropriate date of surgery is determined. Some

authors have suggested that delaying the timing of surgical

intervention enhances results.22 ! ,224 Based on clinical expe­

rience, we believe tllat surgery should be delayed until knee

motion and effusion are normalized. Effective preoperative

rehabilitation followed by an accelerated postoperative pro­

granl appears to achieve the best results with minimal complications.

ACL Rehabilitation Goals: Phase 0 (Preoperative Phase)

• Explain the surgical procedure

• Explain the course of postoperative rehabilitation

• Determine the date of surgery

Postoperative ACL rehabilitation begins on the first day after surgery. The goals of phase J, the immediate postoper­

ative phase, are to reduce pain and swel ling, regain full pas­

sive knee extension, re-establish quadriceps control, and

restore patellar mobility and independent ambulation.

A commercial cold wrap is applied to the knee while tile

patient is in the recovery room to reduce pain and swelling.

Quadriceps muscle contractions and full passive knee exer­

cises are emphasized to prevent the development of arthro­

fibrosis on the first post operative day. A postoperative

hinged knee brace is worn and locked at 0° knee extension

during ambulation . Weight bearing is permitted as toler­

ated witll the assistance of two crutches.

ACL Rehabilitation Goals: Phase I (Immediate Postoperative Phase)-Week 1

• Reduce pain

• Reduce swelling • Regain full passive knee extension

• Re-establish quadriceps control

• Restore patellar mobility

• Restore· independent ambulation

These primary goals continue through the first week of

postoperative rehabilitation. To reduce pain and swelling,

tile patient wears the continuous cold unit as much as

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 567

possible. The rehabilitation specialist and the patient per­

form patellar mobilizations to prevent the negative effects

of immobilization . In addition, the patient's knee flexion

ROM is gradually increased. By postoperative day 5, the

patient should have 90° of knee flexion; by day. 7, the per­

son should have at least 1 00° of knee flexion. CKC func­

tional training also begins during the first ' week with

exercises that include minisquats (0° to 40° ), balance drills,

and proprioceptive training activities.

Phase II, the early rehabilitation phase, includes weeks

2 to 4. The goals during this phase include maintaining full

passive knee extension, gradually increasing knee flexion,

and restoring proprioception . Restoration of full passive

knee extension should be emphasized early in the postoper­

ative program. Some patients may show hyperextension of

the tibiofemoral joint. Whether full hyperextension should

be restored is the subject of debate. Some authors have

reported that restoring full hyperextension does not affect

ligament stability.269 It is suggested that, in the clinic, the

patient regain only 5° to 7° of hyperextension through

stretching techniques; the remaining hyperextension may

be achieved through functional activities. The authors

believe that this allows the patient to gain a greater degree

of neuromuscular control rather than clinically stretching

to excessive motion.

ACL Rehabilitation Goals: Phase I I-Weeks 2-4

• Maintain full passive knee extension

• Increase knee flexion

• Restore proprioception

• Restore muscle strength and endurance

• Achieve full weight bearing

• Begin gait training

• Begin functional exercises

Knee flexion is increased gradually during the early reha­

bilitative phase. The rate of progression is based on the

patient'S unique response to surgery. If substantial effusion

is present, range of motion is advanced at a slower rate,

allowing adequate time for the swelling to subside. Also,

the rate of knee flexion motion is adjusted based on the

patient's ligamentous end feel. A firm end feel indicates

an aggressive rate of progress, and stretching is appropriate .

Conversely, when a patient has a capsular, or sofi:, end feel,

a slower rate of progression is suggested.

Muscle training is progressed with OKC and CKC exer­

cises during this phase. Electrical muscle stimulation is

applied to the quadriceps muscle during therapeutic exercise

to facilitate active quadriceps contraction and to prevent

muscle inhibition from pain and swelling.270,27 1 Other exer­

cises to enhance proprioception and weight distribution also

are initiated. A critical goal during week 2 is to train the

patient to assume full weight bearing on the involved leg.

A force platform ofi:en is used to assess the exact percentage

of body weight used by the involved limb and to provide bio­

feedback training. OKC exercises initiated at this time

include hlp abduction and adduction and knee extension in

a restricted ROM (90° to 40° ) . This restricted range has been

shown to reduce strain on the healing ACL graft.24

In weeks 3 to 4, functional exercise drills to strengthen the

lower extremity are incorporated . Such activities include lat­

eral step-ups, front step-downs, lateral lunges, and lateral cone step-overs. The patient rides a stationary bike to stimu­

late ROM . Lastly, as the incision heals, a pool program is

begun to facilitate proper gait training and to provide a safe

environment for initiation of more advanced drills.272

Phase I I I , the intermediate phase, usually begins by week

4 and continues tllrough week 1 0 . Progression is based on

tlle accomplishment of the specific goals of previous phases;

therefore, the actual time frame varies from patient to

patient. The goals in phase I I I are to establish fu ll normal

ROM while improving muscular strength, proprioception, and neuromuscular control. The strengthening program is

progressed in weight, repetitions, and sets. CKC exercises

are advanced to include tlle leg press ( l 00° to 0° ) and wall

squats (0° to 70° ) . Proprioception and functional exercises

are advanced to enhance dynamic joint stability; such drills

include squatting on an unstable platform and lateral lunges

with a resistance cord attached to the patient's waist. Ball

tosses are incorporated into the proproception exercises as

the patient tolerates, to remove the patient'S conscious

awareness of joint position . Aquatic therapy is used during

this phase to allow the patient to begin early running and

agility drills in tlle pool. The buoyancy of the water assists

the patient by reducing tlle percentage of body weight, and

thus the loads, applied to the lower extremity.

ACL Rehabil itation Goals: Phase II I {Intermediate Phase)-Weeks 4-1 0

• Establish normal range of motion

• Re-establish neuromuscular control

• Improve strength and endurance • Improve proprioception

Phase TV, the advanced activity phase llsually is initiated

at week 1 0 and progresses until week 1 6 . The patient must

have met specific criteria to begin this phase. The patient

must pass a clinical exanlination that shows full active

ROM and satisfactory isokinetic strengtll . The muscle per­

formance characteristics of an ACL-reconstructed knee

have been documented by Wilk et a1 .273 At 1 0 to 1 2 weeks,

the patient usually demonstrates a 30% deficit in the bilat­

eral peak torque comparison of the quadriceps muscle

group and a 0% to 1 0% deficit of the hamstring muscle

568 CHAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

group. Once these predetermined criteria have been met,

advanced, sport-specific drills can be started.

ACL Rehabilitation Goals: Phase IV (Advanced Activity)-Weeks 1 0-1 6

• Begin aggressive strengthening

• Introduce neuromuscular control drills

• Initiate advanced activity-specific drills

During the advanced activity phase, emphasis is placed on

aggressive strengtllening exercises, neuromuscular control

drills, and sport-specific training activities . Strengiliening

exercises are progressed to high weight, low repetition sets

for muscle hypertrophy. Plyometric dlills are used to enhance dynamic joint stability and neuromuscular control; such exer­

cises include the plyometric leg press and double leg box

jumps. Perturbation training also is used to enhance neuro­

muscular con trol . The patien t is trained to perform these exer­

cises with a knee flexion angle of l 5° to 300 to enhance EMG . .

f I d . 24 35 274 I ddi ' actIVIty 0 t le qua nceps. " n a tIon, a flat-ground

running program is initiated, including agility drills such as

backward fll1U1ing, side shuffles, and cariocas . The patient's

return to sport-specific drills progresses mrough a series of

transitional dlills designed to challenge tile neuromuscular

system . Pool running is performed before flat-ground run­

ning. Backward running and lateral running are performed

before forward running. Plyometrics are performed before

running and cutting drills to train me lower extremity to dissi­

pate ground reaction forces. These progressions ensure that

the patient has ample time to develop tile neuromuscular con­

trol and dynamic stabilization needed to perform these drills.

Phase V the return to activity phase, typically begins at post­

operative week 1 6. Further isokinetic tests275,276 and hop t 276-278 C d d

. I tI tI . ests are penorme to etermme w le ler le patIent

can return to sports and work activities . Functional motor pat­

terns are progressed mrough plyometric and agility drills to

accelerate sport- or activity-specific training activities . Once

the patient has demonstrated normal movement patterns and

the specific criteria have been satisfied, tile individual may

begin practice activities. The patient is monitored closely until

the individual participates in full competition. Normal return

to sports activities occurs at about 6 montlls for me accelerated

patient and 6 to 9 montlls for general ortllopedic patients.

ACL Rehabilitation Goals: Phase V (Return to Activity)-Weeks 1 6+

• Assess for functional motor patterns

• Ensure normal movement patterns

• Begin sport practices

Posterior Cruciate Ligament Injuries

Nonoperative Management PCL injuries occur less frequently than ACL injuries.

Isolated injury to the PCL does not produce tile same

degree of functional instability and disability seen Witll

i nj ury to the ACL. Many patients with an isolated PCL

injury can return to tlleir previous level of function witll

minimal symptoms. The level of function and patient satis­

faction appear to be related to the ability of the quadriceps

to stabilize me knee dynamical ly. Parolie and Bergfeld 16 1

reported tile long-term results of 25 patients with PCL

injuries who were managed without surgery. All patients

who returned to tlleir previous level of function and were

satisfied wim meir results had isokinetic quadriceps torque

values on tile involved side greater than 1 00% of those on

me non involved side . Conversely, patients who were not

satisfied Witll meir knees had isokinetic torque values on

the involved side tllat were less tllaIl 1 00% of tllOse on the

noninvolved side . The level of function after PCL injury

does not appear to be related to me degree of instabil­

ity. 1 6 1 , 1 69 It should be noted, however, that long-term fol­

low-up of PCL injuries reveals the development of

progressive pain and degeneration of the patellofemoral

joint and medial compartment of tile tibiofemoral joint. 168

This likely is due to altered armrokinematics in the PCL­

deficient knee.

Treatment after acute injury to the PCL is similar to the

management of acute ACL injuries. It should focus on

resolving inflammation, restoring ROM, and regaining

motor control of the knee . Cold and compression are used

to reduce pain and swelling. ROM exercises are performed

to restore motion, which should improve as pain and

swelling subside . Isometric exercises for the quadriceps,

including quadriceps sets and SLRs are used to minimize

quadriceps atrophy. Hamstring exercises are avoided at this

time, because mey contribute to increased posterior laxity.

Also, the hamstrings do not appear to be as susceptible as

me quadriceps to disuse atrophy. Assistive devices are used

for ambulation while me knee is still actively inflamed.

The use of assistive devices is discontinued when tile patient

has regained full extension witll0ut a quadriceps lag and

CaIl walk normally, wimout gait deviations.

More aggressive rehabilitation can begin once inflamma­

tion has resolved and full ROM has been restored . The

emphasis at this time is on improving tile endurance and

strength of tile quadriceps muscles. OKC knee extension

exercises should be modified if tile patient complains of

pain or crepitus. CKC exercises are initiated and progressed

as tolerated to improve me endurance and strength of tile

muscles of .the lower extremity in functional patterns.

OKC knee flexion exercises should be avoided, because

mey contribute to increased posterior tibial translation. For

patients with a PCL-deficient knee, tile hamstrings are

strengthened by performing open chain hip extension with

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 569

the knee near terminal extension, which minimizes posterior

tibial translation at the knee caused by the hamstrings. Dur­

ing CKC exercises, the hamstrings fi.ll1ction to counteract

the flexion moment arm at the hip. Their effect ( i .e . , produc­

ing posterior tibial translation of the knee) is offse� by simul­

taneous activity of the quadriceps. Proprioceptive training

for the PCL-deficient knee should emphasize recruitment

of the quadriceps to control posterior translation of the tibia

dynamically. The patient is progressed from walking to jog­

ging-running, acceleration-deceleration, sprinting, jumping,

cutting, pivoting, and twisting as tolerated.

Generally, patients with a PCL-deficient knee do not com­

plain of instabil ity during physical activity, and a functional

brace usually is not necessary. If a patient with a PCL-deficient

knee does require a functional knee brace, one that is specifi­

cally designed for a PCL-deficient knee shouJd be chosen.

Most functional knee braces are designed for an ACL-defi­

cient knee and do not benefit a patient with a PCL-deficient

knee. Many patients with a PCL-deficient knee complain of

patellofemoral symptoms, and these individuals may benefit

from the use of a neoprene patellar sleeve.

Because of the tendency for progressive deterioration of

the anterior and medial compartments of the knee, patients

with a PCL-deficient knee should be educated to avoid

activities that cause pain and swelling. Repetitive activities

that involve high loading of the patellofemoral and tibiofe­

moral joints may accelerate this degenerative process and

should be avoided.

Surgical Management Clinicians must take into account a number of important

variables when deciding how best to manage a PCL injury.

These include the type of injury; whether associated struc­

tures have been damaged; the patient's symptoms, activity

level, goals, and expectations; and the acuity or chronicity

of the injury. The goal of treatment is to restore the stabil­

ity and normal kinematics of the knee and to allow the

patient to return to the preinjury level of activity. The best

way to achieve this is still the subject of debate.

For interstitial tears of the PCL, the decision to perform

surgery is based on the degree of resuJting functional instabil­

ity and injuries to associated ligamentous structures. Surgical

reconstruction is recommended for isolated PCL disruptions

that result in greater than 1 0 mm of increased posterior tibial

translation compared to the noninvolved side or when injury

to the PCL is accompanied by injury to other ligamentous

su·uctures. Acute repair of a PCL avulsed fi'om the bone or

avulsed with bone may be possible with a single screw or suture technique. Most series have shown that acute recon­

structions do better than chronic cases, because the potential

for stretching out of secondary restraints increases with time .

It is important to note that a posterior drawer greater than

1 5 mm indicates combined injury to the PCL and posterolat­

eral structures.46 An occult injury to the posterolateral corner

shoulder be evaluated and concomitantly treated.

PCL tears can be reconstructed using an open or an

arthroscopic technique. The authors prefer to perform

PCL reconstruction using an artllroscopically assisted tech­

nique; although it is technically more demanding, it is

believed to reduce operative morbidity and to hold promise

for improved clinical results. As with reconstruction of the

ACL, PCL reconstruction has been performed using a vari­

ety of graft materials, including patellar and Achilles tendon

allografts, patellar tendon, fascia lata, medial head of the

gastrocnemius, semitendinosus-gracilis, and meniscus auto­

grafts, and synthetic replacements. Procedures in which the

medial head of the gastrocnemius,55,279-283 the semitendi­

nosus-gracilis,280,28 I the iliotibial band,282 the menis­

cus,283,284 Gore-Tex synthetic ligament,285 and primary

unaugmented repair286-288 were used all have failed to pro­

duce consistent, objective results.

One technique for PCL reconstruction consists of

reproducing the anterolateral bundle of the ligament,

because this is the largest and strongest band and it func­tions primarily with the knee in flexion. The procedure is

performed by drilling the tibial tunnel so that it reproduces

the distolateral portion of the tibial insertion site and dril­

ling the femoral tunnel so that it reproduces the anterior

portion of the femoral insertion site . An Achilles tendon

allograft is passed through the femoral and tibial tunnels.

The autllors prefer to use an Achilles tendon allograft

because of its length and strength, availability, lack of mor­

bidity to the patient, and ease of passage; one end of the

graft is without a bony block and can easily be passed

through the acute angle required to go fi'om the femoral

to the tibial tunnel. The femoral side, which includes the

Achilles bone plug, is fixed with an interference screw, and the tibial side is fixed to the tibia with a screw and soft

tissue spiked washer ( Figure 1 6-3 1 ) . Although this type of reconstruction may reduce poste­

rior tibial translation at the time of surgery, increased laxity

often is noted clinically postoperatively. Recent anatomical

and biomechanical studies have shown that the two bundles of the PCL have different roles in the normal arthrokine­

matics of the knee . The anterolateral bundle becomes taut

in flexion, and the posteromedial bundle becomes taut in

extension. For tllis reason, a double bundle technique

recently has been advocated for reconstruction of tile

PCL. This procedure, which uses two separate grafts to

restore both tlle anterolateral and posteromedial bundles

of the PCL, requires two femoral tunnels and one common

tibial tunnel . During reconstruction, tile anterolateral

bundle is tensioned in flexion, and the posteromedial bun­

dle is tensioned in extension. Harner et a1 . 289 recently

reported that double bundle reconstruction more closely

restores the normal tibial translation and biomechanics

of tlle knee tllan We single bundle technique. Several

authors have described tlle double bundle procedure in

detail. 33,239,289,290 Nonetheless, tlle advantages of the

double bundle technique have not been confirmed in the

570 CHAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

B

c

literature, and much debate still exists over the best tech­nique for PCL reconstruction .

Postoperative Management for Reconstruction of the Posterior Cruciate Ligament Little is known about the healing and maturation of PCL grafts. Bosch et al.29 1 studied PCL graft fixation i n sheep using a free patellar tendon graft and demonstrated good bone to bone incorporation at 6 weeks. I n their study, post­operative management consisted of immediate partial weight bearing and range of motion beginning 2 weeks after surgery. Clancy et al . 253 demonstrated revascularization of free patel­lar tendon grafts 8 weeks after surgery in rhesus monkeys. As yet, no studies on graft fixation and incorporation after PCL reconstruction have been done in humans.

The rehabilitation program after PCL reconstruction has evolved dramatically over the past several years as a result of advances in researchers' understanding of tl1e anatomy and biomechanics of tl1e knee and in surgical techniques.

The goals of rehabilitation include restoring full range of knee motion, preventing wear of the articular cartilage, grad­ually increasing the stress applied to the healing PCL graft, and improving dynamic stabilization oftl1e musculature about the knee joint. Rehabilitation of PCL injuries focuses on

Figure 16-31 Posterior cruciate ligament ( peL) reconstruction.

A, peL reconstruction is performed with an Achilles tendon allograft passed through the femoral and tibial tunnels. B, The femoral side is fixed with an interference screw. e, The tibial side is fixed with a soft tissue spiked washer and screw. (From Zachazewski IE, Magee DJ , Quillen WS, editors: Athletic injuries and rehabilitation,

p 670, Philadelphia, 1 996, WB Saunders . )

rega.ll1l11g quadriceps strengtl1 and control . In fact, earlier quadriceps contraction in the gait cycle can increase dynamic stability in tl1e knee enough to overcome the instability from an incompetent PCL.292 Rehabilitation therefore focuses on regaining or exceeding normal quadriceps strength.293

Overall Goals in pel Rehabilitation

• Restore full range of motion

• Prevent excess articular cartilage wear

• Gradually increase stress to posterior crucial ligament

• Improve dynamic stabilization

• Regain quadriceps strength

• Minimize posterior tibial translation

It is important to mml lTIlZe posterior tibial translation during rehabilitation?94 This is accomplished by protecting against gravity-induced posterior sag and by avoiding OKC han1string· exercises. CKC exercises, such as the squat, pro­duce less tibiofemoral shear force. OKC quadriceps extension exercises at 70° to 0° are used because of the anterior pull of the patellar tendon on tl1e tibia.

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 571

The authors' current program consists of five phases

designed to progress the patient gradually to full, unre­stricted activities by 6 to 7 months after surgery. The proto­

col gradually normalizes hemarthrosis, ROM, and strength

while preventing degeneration of the articular . cartilage at

the patellofemoral and tibiofemoral joints.

Immediately after surgery, the knee is wrapped with a

compression dressing and continuous cryotherapy ( Polar

Care, Breg Vista, CAl is applied. The patient uses a drop­

lock knee brace that is locked into extension. Arnbulation

initially involves two crutches and approximately 50% weight bearing. The brace may be unlocked into flexion

when the patient sits or performs exercises. Full passive

knee extension should be restored soon after surgery to

prevent the development of arthrofibrosis within the joint.

Range of motion and patellar mobilizations, particularly

superior patellar glides, are performed four to five times

throughout the day to help restore full knee extension .

Knee motion should be progressed gradually to 900 by

the end of week 1 . Exercises are also performed, incl uding

quadriceps setting; isometric knee extension at 00, 200, 400 , and 600 of knee extension; and straight leg raises into

flexion, abduction, and adduction. Electrical muscle stimu­

lation is applied in conjunction with these exercises to facil­

itate a quadriceps contraction 270,295,296 Isolated hamstring

exercises are contraindicated for the first 8 weeks because of

the large posterior shear force generated with hamstring

contraction. Cryotherapy commonly is used for 1 5 minutes

before and after treatment to control pain and edema.

pel Rehabil itation Goals: Phase I-Weeks 0-1

• Reduce swelling

• Protect the knee in a brace (locked in extension except when

exercising)

• Obtain 900 flexion by the end of week 1

• Obtain 50% weight bearing

• Regain full passive knee extension

• Maintain patellar mobility

Range of motion and weight bearing are progressed

gradually during weeks 2 to 6. Motion increases from

00 to 900 during week 1 ; 00 to 1 050 by week 2; 00 to

1 1 50 by week 4; and up to 1250 by the end of weeks 5 to

6. Weight bearing is progressed gradually to full weight

bearing by week 3. At 14 days the patient begins to ambu­

late with one crutch, which is discontinued at day 2 1 . Quadriceps strengthening activities are progressed to

include OKC knee extension from 600 to 00 and the

CKC leg press from 600 to 00 during week 2. Minisquats

are also performed from 0° to 45° . Because the loss of pro­

prioception after PCL injury is well documented,297 the

authors begin proprioceptive drills, such as minisquats on

an unstable platform ( Biodex Stability System, Biodex,

Shirley, NY), soon after surgery. Neuromuscular control drills that train muscular co-activation for dynamic stabili­

zation are also incorporated at this time. Particular drills

initiated by week 4 are lateral step-overs performed over

cones and lateral lunges. Perturbation training is initiated

at this time and is emphasized throughout the program.

The stationary bicycle may be used for quadriceps strength­

ening, motion stimulation, and cardiovascular training when range of motion permits. Also at this time, an aquatic

therapy program consisting of pool walking and lower

extremity exercise is added. Swimming is permitted

between week 6 and week 7, with the precaution of kicking

with a straight leg only. All CKC exercises are progressed by

weeks 6 to 8 to include lateral step-ups, front step-downs,

stair climbing machines, and advanced proprioceptive and

neuromuscular control drills. At 8 weeks, resisted ham­

string contractions are initiated from 00 to 60° with light resistance. Pool running begins at week 1 2 to prepare the

patient for dry land running and agility drills, including lat­

eral, backward, and forward movements.

pel Rehabilitation Goals: Phase II-Weeks 2-1 2

• Progress quadriceps strengthening activities

• Proprioceptive drills

• Reinforce neuromuscular control • Initiation of pertubation training

The light activity phase begins around 3 to 4 months.

Emphasis is placed on advancing strengthening drills,

continuing neuromuscular control drills, and beginning

sport- or activity-specific training drills. Plyometric exer­

cises are used to enhance dynamic joint stabilization and

neuromuscular control. The rapid dynamic loading of tlle

musculature during plyometric drills helps train the stretch­shortening cycle of the musculature. Plyometric drills are

progressed from the leg press machine to flat-ground to box j umps to single-leg jumps. Agility drills and sport- or

activity-specific training drills may be incorporated at this

time for the patient. Ifsatisfactory results are seen on the clin­

ical examination, tlle return to sport phase is initiated and

a running program on dry land begins at 4 to 5 months and

gradually progresses in intensity for 4 to 6 weeks.

pel Rehabilitation Goals: Phase I I I (Light Activity Phase) -Weeks 1 3-20

• Emphasize strengthening, neuromuscular control training

• Begin sport- or activity-specific training drills

• Begin plyometric training

572 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

PCl Rehabilitation Goals: Phase IV (Return to Sport) -Weeks 21 +

• Begin running on dry land

• Gradual progression of training intensity

The authors periodically assess the knee laxity of patients

with a reconstructed PCL throughout the program .

A KT2000 arthrometer (MEDmetric, San Diego, CA) is

used to assess the anteroposterior laxity of the knee joint

at 2, 4, 6, 8, and 1 2 weeks and at 4, 6, 1 2, and 24 months

after surgery. The test is performed at the quadriceps-neu­

tral angle to ensure that anteroposterior laxity is measured

accurately. Serial assessment of knee laxity is useful to the

rehabilitation specialist for evaluating the integrity of the

graft . The rehabilitation program is assessed on the basis

of the results of the arthrometric testing and then is

adjusted accordingly.

In the authors' experience, patients typically can return

to noncontact sports at 5 . 5 to 6 months after surgery and

to contact sports at 6 to 7 months. The authors tend to

be more cautious with skiers because of the highly dynamic

nature of the sport; they generally permit skiing at 8 to

9 months after surgery.

Medial Collateral Ligament Injuries

The philosophy for managing isolated MCL 1l1Juries has

changed as a result of basic scientific and clinical studies.

In the past, many of these injuries were treated with surgi­

cal repair followed by immobilization for 6 weeks. Studies in rabbits by Anderson et al .76 and Weiss et al.298 demon­

strated that isolated MCL injuries heal when the ACL is

intact. Similar findings were noted in clinical studies that

demonstrated no difference in stability or function between

patients with isolated MCL injuries who were treated non­

operatively and those who had surgery. 1 54, 1 74, 1 77,299

Isolated MCL tears heal well without surgery, regardless

of the degree of injury or the patient's age or activity

level . 1 73- 1 79 Usually some residual valgus laxity can be eli­

cited on physical examination after a grade II or grade I I I

injury, because the ligament may heal in a lengthened state,

but this has little effect on knee function. Patients with

combined MCL-ACL injuries, however, may require recon­struction of the ACL with or without repair of tl1e MCL to

restore stability and function to the knee. Reconstruction

of tile ACL alone for patients with a combined ACL­

MCL injury may restore enough stability to the knee to

allow the MCL to heal .

Acute treatment of isolated MCL injuries depends

on the stability of the joint. Grade I and grade I I MCL

sprains that are stable with valgus stress testing are treated

symptomatically Witllout tile use of a rehabilitation brace .

Patients with isolated grade I I I MCL injuries who are

unstable with valgus stress testing and who have a soft

end point are treated with a hinged rehabilitation brace

for 4 to 6 weeks. The brace typically is set to permit 0° to

90° of motion. The brace controls valgus stresses, allowing the ligament to heal while permitting limited motion of the

knee. Treatment of acute MCL injuries should include the use

of cold and compression to control pain and swelling. Early

range of motion in the pain-free range is encouraged to

facilitate healing and prevent the development of a stiff

knee . Transverse friction massage and pulsed ultrasound

to tile ligament may be beneficial to stimulate healing and

orientation of tile ligament fi bers and to prevent tile forma­

tion of adhesions. Isometric exercises for the quadriceps

and hamstrings are initiated to minimize disuse atrophy. Assistive devices are used for ambulation until tile patient

demonstrates fulJ extension of tile knee Witllout all extensor

lag and call walk normally, without gait deviations.

Once inflammation has resolved and ROM has improved,

tl1e patient can begin OKC and CKC exercises to increase

tile endurance and strength of tile quadriceps and hamstring

muscles. Exercises are progressed as tolerated, witll care

taken to prevent tile development of patellofemoral symp­

toms. As strength and endurance improve, tl1e patient pro­

gresses tllrough functional activities to enhance dynamic

stability of the knee and to prepare for return to activity.

Patients returning to contact sports may use a functional

knee brace to reduce tile risk of reinjury. For MCL injuries,

tile brace should have good medial and lateral stays to

control varus-valgus rotation .

lateral Collateral Ligament Injuries

The treatment of acute, isolated LCL injuries depends on the stability of tl1e joint. Grade I and grade I I LCL sprains

that are stable with varus stress testing are treated symp­

tomatically without the use of a rehabilitation brace .

Patients with isolated grade I I I LCL injuries who are unsta­

ble with varus stress testing and who have a soft end point

are treated with a hinged rehabilitation brace for 4 to

6 weeks. The brace usually is set to permit 0° to 90° of

motion. The brace controls varus stresses, allowing tile lig­

ament to heal while permitting limited motioh of the knee.

Treatment of acute LCL injuries is similar to that for MCL injuries. Cold and compression are used to control

pain and swelling. Early range of motion in the pain-free

range is encouraged to facilitate healing and to prevent

the development of a stiff knee. Isometric exercises for

the quadriceps and hamstrings are initiated to minimize

disuse atrophy. Assistive devices are used for ambulation

until the patient demonstrates full extension of tile knee

without an extensor lag and can walk normally, without gait

Knee: Ligamentous and Patellar Tendon Injuries • CHAPTER 1 6 573

deviations. Once inflammation has resolved and ROM

has improved, the patient can begin OKC and CKC exer­

cises to increase the endurance and strength of the quadri­

ceps and hamstring muscles. As strength and endurance

improve, the patient is progressed through functional activ­

ities to enhance the dynamic stability of the kliee and to

prepare for return to activity. Patients returning .to contact

sports may use a functional brace with good medial and

lateral support to reduce the risk of rein jury.

Surgery for isolated grade I I I LCL injuries is recom­

mended for patients with chronic varus instability that

affects their daily function and for patients who want to

continue sports activities. Surgery also is recommended

for injuries involving a bony avulsion that is displaced more

than 3 mm. Reports on the results of LCL reconstruction

are lacking. Reconstruction for acute or chronic LCL inju­

ries usually is reserved for knee injuries involving multiple

ligaments (see the following section) .

The authors' technique for reconstruction of a chroni­

cally LCL-deficient knee depends on the acuity and severity of the injury. With an acute LCL tear, the ligament some­

times can be reattached to its insertion with suture anchors,

or a primary repair of the ligament can be performed.

Often, however, the ligament is torn through its midsub­

stance and cannot hold sutures for repair. In these cases,

as well as in the chronically LCL-deficient knee, the authors

use an Achilles tendon allograft for reconstruction of the

LCL. The bone plug of the Achilles tendon graft is placed

in the fibular head and is fixed with an interference screw.

The soft tissue end of the graft is fixed to the anatomical

insertion of the LCL on the femoral epicondyle with suture

anchors. Care must be taken to avoid putting excessive

stress on the graft as the knee is taken through a range of

motion . Nonisometric placement of the graft can lead to

stretching or tearing. The LCL remnants are sutured to

the graft to provide added healing potential and possibly

proprioceptive function 300

After LCL reconstruction, patients are placed in a post­

operative brace for 4 to 6 weeks to minimize varus stress. During this period, limited ROM exercises from 0° to 90°

are performed. During the first postoperative week, isomet­

ric quadriceps and hamstrings exercises are initiated. A par­

tial weight-bearing gait is used for 4 to 6 weeks after

surgery to minimize stress on the graft. The authors have

found that early, full weight bearing, particularly in the knee

that demonstrates a varus thrust, leads to increased varus

laxity. After 6 weeks, the patient is progressed to weight

bearing as tolerated . Assistive devices are discontinued once

the patient has full knee extension without a quadriceps lag

and is able to demonstrate a normal gait pattern .

The rehabilitation brace generally i s discontinued at

6 weeks after surgery. At this time, emphasis is placed on

regaining fu ll range of motion and on developing muscle

function for the lower extremity using OKC and CKC knee

exercises. Proprioceptive activities are initiated to regain

neuromuscular control of the knee . Gradual sports-specific

functional progression allows a return to sports within 6 to

9 months. A functional brace that provides varus stability is

recommended for return to sports.

Multiple-ligament Knee Injuries

Treaunent of multiple-ligament injuries of the knee includes

a wide spectrum of pathology and requires evaluation of

many factors. A knee dislocation can be limb threatening

and is associated with a high incidence of neurological and

vascular injuries. Immediate surgical intervention is neces­

sary if the multiple-ligament injuries are associated with vas­

cular injury or a compartment syndrome. A grossly unstable

knee can be stabilized with an external fixator while these

acute issues are addressed.

Knee dislocations can be low or high energy injuries . Low

velocity injuries often are athletic injuries and have a better

prognosis because fewer vascular injuries are involved. High

velocity injuries have a higher incidence of other organ sys­

tem injuries and neurovascular compromise. However,

ultra-low velocity injuries in patients with a body mass index

(BMI) of 40 or higher may have a very high rate of vascular

injury. 1 89

Many knee dislocations reduce spontaneously. If three or

more ligaments of the knee are injured, a knee dislocation

should be suspected and appropriate neurovascular exami­

nations should be performed.

Based on the work of Taylor et al. 193 on nonoperative

versus operative treaUTIent of knee dislocations, it is reason­

able to conclude that nonoperative management could

result in a functional knee, depending on the patient's

demands. However, most authors support open surgical

techniques to restore stability and attempt to improve filllC­

tional outcome. 1 84,2 2 1 ,30 1 -303 Also, surgical management

of a knee with a multiple-ligament injury may prevent or

delay the onset of arthritis by improving joint stability.

FLillctional deficiency that results from a multiple-ligament

knee injur y must be evaluated relative to the patient's age,

occupation, and recreational interests and the neurovascu­

lar status of the affected extremity before a decision is made

to treat the condition surgically.

When the authors opt for surgical management of this

injury, reconstruction usually is delayed for 3 weeks after

injury to allow soft tissue swelling to decrease. "Sealing"

of the capsular injury occurs within a week, which permits

the use of arthroscopically assisted techniques. Delayed reconstruction can also prevent the risk of arthrofibrosis

by allowing time to regain motion after injury. 1 87 Even so,

early repair ofthe posterolateral corner should be considered

before 3 weeks to allow for the possibility of a primary repair

of these su·uctures. In this case, the posterolateral corner

is repaired in this first stage, and cruciate ligament recon­

struction is performed several weeks later, when motion

has been regained.

574 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

In general , the treatment of each individual ligament

injury is similar to that for an isolated injury of that

ligament. Knees with an MCL injury are braced for the

first 4 to 6 weeks to allow healing preoperatively. Recon­

struction of the cruciate ligaments is then performed

concomitantly. The authors prefer reconstruction using

allograft tissue to reduce surgical time and patient mor­

bidity. Use of allograft tissue also ensures the availability

of graft tissue and minimizes difficulty with graft passage.

The procedure is performed with arthroscopic assistance for the cruciate ligaments, particularly if the injury

involves the ACL, PCL, LCL, and/or posterolateral cor­

ner with the ACL, PCL, or MCL avulsed off the tibial

or femoral insertions .

Postoperative rehabilitation for acute reconstructions

involves early motion and weight bearing with a gradual

restoration of knee flexion. Range of motion is progressed from 0° to 65° on day 5, 0° to 75° on day 7, 0° to 90° on day 1 0, 0° to 1 00° beginning week 2, 0° to U5° begin­

ning week 6, and 0° to 1 25° and beyond beginning week 7. Weight bearing is progressed from 50% body weight at day

7, to 75% body weight at day 1 2 , and finally full weight

bearing by week 4. A brace is used for the first 7 to 8 weeks.

Patients often are fitted for functional knee braces when

the postoperative knee brace is discontinued. CKC exer­

cises are initiated during week 3 with weight shifts and

minisquats and progressed to include the leg press, aquatic

therapy, and bicycle by week 4. Return to functional

activities is allowed beginning witll a walking program at

week 1 2 , progressing to light running by weeks 1 6 to 20, and more aggressive agility drills by 5 to 6 months.

Treatment of Patellar Tendon Injuries

Patellar Tendinopathy

Patellar tendonitis is one of the most common causes

of anterior knee pain in the athletic population. Activities tl1at involve repetitive jumping, such as basketball and

volleyball, have a high rate of patellar tendonitis because

of the repetitive eccentric contractions of the quadriceps

muscle . Theories about the etiology of these injuries vary

and include both intrinsic factors (e .g . , muscle tightness,

strength imbalances) and extrinsic factors (e .g . , sport, train­

ing frequency), and both likely relate to the pathological

development.

The progression of symptoms has been described by

Blazina et a1 .304 and can be classified into four stages. Stage I tendinopathy typically occurs after a recent change

in sports activity or a change in the intensity of the current

sports activity. This stage is characterized by pain that is

experienced after activity. Symptoms do not typically limit

participation at this stage of the patllology. Stage II is char­

acterized by pain at the start of activities that subsides, only

to return as the patient begins to fatigue toward the end of

partICIpation . Stage I I I involves constant symptoms that

limit the activity. Stage IV is defined as tendon rupture.

The stages of pathology defined by Blazina et a1 . 304

correspond well with tlle stages of tendinopatllY defined

by Nirschl . 305 He described an acute period of inflam­

mation of the tendon and paratenon sheath surrounding the tendon (stage I ) . As the chronicity of symptoms

continues, the underlying tendon tissue begins to develop tendinosis, whereas the paratenon continues to show an

inflammatory response (stage I I ) . Eventually tlle pailiology

becomes chronic enough tllat inflammation subsides and

tendinosis of tlle tendon continues (stage I I I . ) To develop

an appropriate treatment program for patellar tendinopa­

thy, it is imperative iliat the clinician ditTerentially diagnose ilie appropriate stage of patllology and treat tlle patient

accordingly.

On clinical examination, ilie patient often is point tender

to palpation at the inferior patellar pole at the patellar ten­don junction. The patient also may have symptoms in the

mid portion or distal attachment of the tendon, although

iliese findings are less common. Resisted quadriceps con­

tI"action may elicit symptoms, and the patient often has

tightness of the quadriceps musculature. Witvrouw et al.44

prospectively evaluated predictive factors in tlle develop­

ment of patellar tendinopathy and reported that ilie most

common factor was tlle loss of quadriceps soft tissue flexi­

bility. M RI studies often show abnormal signals in the

tendon. As previously mentioned, conservative treatment for

patellar tendinopatllY must be appropriate for the stage

and progression of pathology. For patients in stage I and

early stage II tendinopailiy with an acute onset of symp­

toms and pain after activity, treatment aims at reducing

ilie inflammatory response and balancing the strength and

flexibility of the lower extremity. Traditional anti-inflamma­

tory treatments are used, including ice, phonophoresis,

iontophoresis, and nonsteroidal anti- inflammatory medica­

tions. The patient should try to minimize activities that irri­

tate the tendon, but tlle concept of "rest" should be avoided. Instead, ilie patient should continue to work on

enhancing quadriceps strength, lower extremity muscle

balance, and soft tissue flexibility. Abstaining fi·om all activ­

ities and relying on rest and ice often cause further loss of

strengili and flexibility, which can result in a recurrence of

symptoms when activities are resumed.

Nonoperative Treatment The primary goals of rehabilitation are to control the applied loads and create an environment for healing. The

initial treatment consists of phonophoresis, iontophoresis,

stretching exercises, and light strengthening exercises to

stimulate a healing response . High voltage stimulation

and cryotherapy may be used after treatment to reduce pain

and postexercise inflammation. The patient should be cau­

tioned against excessive running or jumping activities.

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 575

Once the patient's symptoms have subsided, an aggressive

stretching and strengthening program is initiated, with

emphasis on eccentric quadriceps contractions. Several

authors encourage the use of eccentric exercise for patellar

tendinopathy to increase the amount of force applied

to the tendon 306·308 A gradual progression th�ough plyo­

metric and running activities precedes the return to full

activity participation. Because poor mechanics often are a

cause of this condition, an analysis of the mechanics of

the activity and proper supervision are critical. The treatment of more chronic stage II and stage I I I

tendinopathies varies greatly from tllat used for the

acute condition. As the chronicity of the pathology pro­

gresses, inflammation subsides and tissue degeneration

occurs, creating a tendinosis rather tllan tendonitis. Thus

anti-inflammatory treatments are avoided, and a healing

environment is encouraged by attempting to stimulate

blood flow to the area. Treatment includes moist heat or

a warm whirlpool, ultrasound, transverse friction massage,

and eccentric strengthening, which places greater stress on the tendon. The patient is encouraged to exercise in an

environment that induces mild microtrauma to the area to

stimulate a healing response . Patients therefore should

experience mild discomfort when performing tlleir work­

outs. The authors recommend that, during exercise, gen­

eral orthopedic patients experience pain tlley rate as 3 to

4 on a 0 to 1 0 VAS pain scale, and athletes experience pain

they rate as 5 to 6.

Anecdotally, one of the authors ( Michael M . Reinold)

believes that applying electrical stimulation to the tendon

to produce a noxious stimulus often is indicated and is

highly effective in creating a healing environment. Neuro­

muscular electrical stimulation ( Russian, 2500 Hz, 50 pps )

is applied surrounding the area of patllology, and tlle cur­

rent is applied at tlle highest level tolerable to tlle patient.

The stimulation is applied for 1 0 to 1 2 minutes, with a

1 0-second duty cycle immediately before initiation of

strengthening exercises. Subjectively, patients report that

their symptoms are decreased and that they are able to per­

form more aggressive exercises during their workout after

application of this noxious stimulus. However, currently

no evidence or research confirms this self-reported patient

Op1l110n.

Surgical Treatment Surgery generally is performed for chronic tendinosis

tllat has not responded to conservative treatment for 3 to

6 months. The surgery typically involves debridement of degenerative tissue, which creates an inflammatory response

and facilitates a healing response . An incision is made over

the area of tendinosis, and dissection is carried down to tlle

underlying tendon. The paratenon is preserved, and the

patellar tendon is divided longitudinally. Degenerative patel­

lar tendon tissue is debrided, and the patellar tendon is

re-approximated with a high tensile strength suture. Several

surgeons advocate additional stimulation of a healing

response by drilling adjacent bone witll a Kirschner wire

( K-wire ) .

Postoperative rehabilitation focuses on minimizing pain

and swelling and gradually restoring strength and range of

motion in tlle knee. Range of motion is initiated immedi­

ately to stimulate healing and collagen tissue organization.

The patient typically achieves full knee extension immedi­

ately, and full knee flexion is restored gradually over the

first 4 to 6 weeks. Aggressive quadriceps strengtllening is

avoided for tlle first 2 months and then slowly integrated

into tlle program. Strengtll is progressed gradually, but

aggressive OKC knee extension is avoided until at least

3 months after surgery. The patient can begin a gradual

running and jumping program at 3 to 4 montlls. Depend­

ing on the extent of pailiology and surgical debridement,

this progression may be furtller delayed for up to 6 months.

Patellar Tendon Rupture

Patellar tendon rupture is a disabling injury tllat results in

disruption of the extensor mechanism and inability to actively obtain and maintain knee extension. Ruptures

(grade I I I strains) often occur in sports as a result of a vio­

lent contraction of the quadriceps muscle as the foot is

planted and the knee moves into flexion, producing an

eccentric contraction of the quadriceps. Forces causing rup­

ture of the patellar tendon typically are greater than 1 7 x

BW.309 I n patients under 40 years of age, tllese forces are

highest at the insertion of the tendon and tllerefore

commonly produce tears at the inferior pole of the patella.

Ruptures of tlle patellar tendon may be more prominent

witll systemic inflammatory disease, diabetes mellitus, or

chronic renal failure . I n iliese patients, rupture of the patel­

lar tendon may more likely occur midsubstance than at the

osteotendinous junction .

One of tlle most commonly observed causative factors in

patellar tendon rupture is chronic patient complaints of

patellar tendinopatllY. Kelly et al . 31 0 reported a correlation

between pre-existing patellar tendinosis and patellar tendon

rupture. The relatively poor vascularity and chronic degen­

eration of tissue associated with patellar tendinosis, com­

bined with repetitive microtrauma, eventually may result

in full rupture of the tissue.

Patients almost always report an acute incident of

rupture and present Witll pain , swelling, and inability to actively extend tlle knee. A palpable defect often is noted

upon examination. The patient also has a visible antalgic

and quadriceps avoidance gait pattern as the hip muscula­

ture attempts to substitute for tlle lack of quadriceps con­

trol. Plain film radiographs are commonly taken in tlle

lateral position. A superiorly orientated patella, or patella

alta, may indicate a rupture of tlle tendon. MRl can con­

firm the diagnosis of a ruptured tendon and can aid the

assessment for concomitant patllology.

576 CHAPTER 1 6 • Knee: ligamentous and Patellar Tendon Injuries

Surgical Management The treatment of an acute tear in the patellar tendon

depends on the extent of the tear. If the patient is able to

perform a straight leg raise without a quadriceps lag ( inabil­

ity to fully extend the knee ) , nonoperative treatment can be

considered. In most cases, however, patellar tendon rup­

ture results in a disruption of the extensor mechanism and

should be repaired surgical ly.

An anterior longitudinal incision permits exposure of

both the patellar tendon and the patella. Because most rup­tures occur at the tendosseus junction at the inferior pole of

the patella, the patellar tendon cannot usually be simply

reapproximated. Instead, three longitudinal drill holes are

made in the patella. A running locking stitch is placed in

the patellar tendon, and sutures are passed from the tendon

through the drill holes in the patella and tied over a bony

bridge at the proximal aspect of the patella. The paratenon of the patella is repaired, and the patient is placed in a knee

immobilizer or cast.

Postoperative Treatment for Patellar Tendon Repair The rehabilitation program followed after patellar tendon

repair is critical to the long-term success of the procedure.

Rehabilitation must protect the healing tendon while grad­

ually returning the patient to functional activities. Tradi­

tional rehabilitation programs involve approximately 6 to

8 weeks of immobilization and unloading of the lower

extremity after surgery. Although this may be appropriate

for patients with poor tissue status, a very active person or

competitive athlete who wants to return to vigorous activ­

ities may risk the development of joint stiffness and arthro­

fibrosis. The authors prefer a program that gradually

progresses range of motion and weight bearing but does

not overload the healing tissue; this is believed to minimize

the risk of complications such as knee flexion limitations,

patella immobility, and patella baja. 3 1 1 The specific pace

of the rehabilitation program is based on the quality of sur­

rounding tissue and the fixation strengths of the repair.

Communication with the surgeon is vital to develop an

appropriate postoperative program .

The immediate postoperative goals include reducing

pain and swelling, restoring patellar mobility, initiating

early, controlled quadriceps muscle contraction, and gradu­

ally restoring range of motion . The patient is instructed to

use a brace locked in extension for ambulation. I mmediate toe touch weight bearing is initiated, progressing to about

25% of body weight by week 2 and 50% of body weight

by week 3. The patient typically progresses to weight bear­

ing as tolerated without crutches by 6 weeks. At this time,

the patient may unlock the brace during ambulation but

is advised to continue wearing the brace for approximately

8 weeks.

The restoration of passive range of motion is one of

the most difficult goals to achieve. Full knee extension is

encouraged immediately after surgery, although flexion is

limited to 30° for the first 5 days and to 45° by the end

of week 1 . Motion is gradually progressed to 60° by week

2, 75° by week 4, and 90° by week 6. The rate of progres­

sion should be carefully monitored, and a continuous

passive motion (CPM) machine may be useful at home .

Range of motion is gradually progressed to 1 05° by week

8, U 5° by week 10 , and at least 1 25° by week 1 2 .

Restoring Flexion After Patellar Tendon Repair

First 5 days 30°

7 Days 45°

1 4 Days 60° 28 Days 75°

42 Days 90° 56 Days 1 05°

70 Days 1 W

84 Days 1 25°

Initial isometric exercises for the quadriceps and other

lower extremity muscles are encouraged. These exercises

include quadriceps setting and multiangle straight leg raises

by the end of week 2 . Use of the pool and gentle cycling

also may be beneficial for the patient when range of motion

permits, typically by 4 to 6 weeks. Gentle CKC exercises,

such as weight shifting and minisquats to 30°, are initiated

during week 4 and progressed to include the leg press, wall

squats, front lunges, and other lower extremity exercises by

weeks 1 0 to 1 2 . Active OKC knee extension is avoided

for the first 8 to 1 2 weeks. Patients who want to begin a

running program are allowed to do so after a satisfactory

clinical examination . Running typically begin� around 5 to

6 months after surgery, with a gradual return to sports

activity at 7 to 9 months.

Assessment of Functional Outcome

Over the past decade, outcome-based research on ortll0pe­

dic problems of the knee has matured. Research that histor­

ically focused on the regional impact of disease (e .g., range

of motion, strength, and pain ) has broadened to include

parameters that characterize the impact of a particular con­

dition on a patient's ability to function in daily life and

the relationship of the condition to the patient's general

health. In tl1is process, specific and standardized outcome

tools have been developed that have been validated to pro­

duce accurate and reproducible assessments of a patient

population.

This change occurred with recognition of populations of

patients witll residual knee laxity who may be able to per­

form at their previous level of activity without symptoms

and would consider themselves to have a good outcome.

Knee: Ligamentous and Patellar Tendon Injuries • C HAPTER 1 6 577

If outcomes were determined on the basis of joint stability,

however, these patients would be classified as having a poor

outcome. Conversely, patients may have a good outcome in

terms of joint stability but a poor outcome in terms of func­

tional limitations and disability for various reason�, such as

pain, apprehension, fear of reinjury, and lack of confidence. Accurate assessment of outcomes after knee injury now

requires both measures of knee stabil ity, strength, and

motion and assessment of patients' perspective on the impact of the injury on their level of function . In this way,

patient-based subjective assessments are combined with

objective measures to produce a useful gauge of success.

The tools for making these assessments also have

matured in the past decade. Various measures of question­

naire validity are expected before an outcome test is used.

Test-test reliability ( reproducibility), responsiveness (ability

to detect clinically important change), and construct valid­

ity are usually defined for each outcome tool.

Successful application of these tools to assess functional

outcome requires an understanding of the patient popula­

tion and the research question at hand .3 1 2 An instrument

validated for ODe population may not be the correct tool to measure a different population. The Western Ontario

and McMaster Universities (WOMAC) Osteoarthritis

Index, for example, was developed and validated to assess

osteoarthritis outcomes in a relatively older population. 3 1 3

The usefulness of its comparisons in a population o f youn­

ger patients with knee instability is uncertain.

Knee Stability and Function

Historically, outcome studies related to treatment of knee

ligament injuries focused on reporting physical impairment

of the knee, including limitations in range of motion,

strength, and stability. The relationship between physical

impairment of the knee and functional l imitations and dis­

ability experienced by the patient has been the subject of

research .

It has been hypothesized that deficits in range of

motion, strength, and stability result in increased levels of

functional limitations and disability. Snyder-Mackler

et al .27 1 demonsu'ated a significant relationship between

isometric quadriceps peak torque and gait abnormalities.

Decreased levels of isometric quadriceps peak torque were

associated with an increased angle of knee flexion during

gait. Wilk et a1 278 demonstrated a positive correlation between isokinetic knee extension peak torque at 1 800/

sec and 3000/sec and a Modified Cincinnati Knee Rating

Score. Lephan et a!. 14 failed to demonstrate a significant

relationship between isokinetic peak torque and torque

acceleration energy for the quadriceps and hamstrings at

600/sec and 2700/sec and physical performance tests,

including the shuttle run, carioca, and co-contraction semi­

circular run. Furthermore, no relationship was found

between these isokinetic parameters and the Iowa Athletic

Knee Rating Scale. Research is ongoing to clarify the rela­

tionship between isometric and isokinetic strength of the

quadriceps and hamstrings and functional l imitations and

disability experienced by patients.

It has been assumed that increased laxity, measured

manually or with instruments such as the KTI 000, results

in greater functional limitations and disability; however,

tIlis has not always been found to be the case. Lephart

et al. 1 4 reported a nonsignificant relationship between tile

Iowa Athletic Knee Rating Scale score and increased ante­

rior translation of the tibia measured with the KTI 000.

A variety of functional tests have been proposed to assess

outcome after knee ligament injury and/or surgery. Tegner

et al.3 1 4 studied the one-legged hop, running in a figure­

of-eight, running up and down a spiral staircase, and

running up and down a slope in 26 individuals with an

ACL-deficient knee and 66 uninjured soccer players. The

results indicated significant performance deficits in indivi­

duals with an ACL-deficient knee compared to the unin­

jured soccer players.

Barber et a!. 3 1 5 evaluated the one-legged hop for dis­

tance, one-legged vertical jump, one-legged timed hop,

shuttle run with no pivot, and shuttle run with pivot to pre­

dict lower extremity functional limitations in individuals

witll an ACL-deficient knee . Significant differences were

found for ACL-deficient subjects compared to a normal

group of subjects for all tests except the shuttle run Witll

a pivot. The vertical j ump and shuttle run tests were not

capable of detecting functional limitations in the ACL­

deficient subjects. For tile one-legged hop tests, 50% of

patients performed normally, but all reported episodes

of giving way during high force activities, indicating a lack

of sensitivity of such tests to identifying functional limita­

tions in these ACL-deficient patients.

Lephart et a1 . 1 4 demonstrated a significant relationship

between disability as defined by tile Iowa Athletic Knee

Rating Scale and performance time on the shuttle run, cari­

oca, and semicircular co-contraction test. Also, those who

were able to return to preinjury levels of activity demon­

strated significantly better times on the functional perfor­

mance tests than those who were unable to return to tlleir

prior level of activity.

Wilk et al .278 found weak positive correlations between

the Modified Cincinnati Knee Rating Score and the one­

legged hop for distance, one- legged hop for time, and

one-legged crossover test. Their data demonstrate a posi­

tive relationship between functional limitations and disabil­

ity as measured Witll the Modified Cincinnati Knee Rating Score and tile patient's self- rating on a scale of 0 to 1 00

for tile hop index and tile vertical jump index. The hop

index is defmed as the distance hopped on the involved

leg divided by the noninvolved leg multiplied by 1 00.

The vertical jump index is calculated similarly.

I t appears tllat functional performance tests may be bet­

ter predictors of functional limitations and disability than

578 C HAPTER 1 6 • Knee: Ligamentous and Patellar Tendon Injuries

measurements of physical impairment after knee ligament

injury. Deficits in functional performance tests probably

would result in functional limitations and disability for a

patient. Functional performance tests that reproduce the

stresses and sU'ains on the knee that occur during activities

may be more likely to demonstrate functional limitations

and disability. For example, carioca that involves a cross­

cutting maneuver reproduces the pivot shift associated with

anterolateral instability. This maneuver would be expected

to be more stressful than a one-legged hop for distance in

an individual with an ACL-deficient knee. Additional

research is needed to identify functional performance tests

that can accurately predict functional limitations and dis­

ability after a knee ligament injury.

Functional limitations and disability experienced by a

patient after a knee ligament injury may have multiple

causes. Disability may be related to a combination of fac·

tors, such as the type and extent of injury, symptoms, and

physical impairment and to psychological factors, such as

apprehension, lack of confidence, and fear of reinjury. This

diversity has led researchers to use a combination of quality

of life and disease-specific evaluation tools.

Multiple measures of patient outcomes have been used

to measure clinical success. Questionnaires can be used to

measure general health status, pain, functional status, or

patient satisfaction. Physiological outcomes, utilization

measures, or cost measures can also be defined as end points. Assessment tools can be driven by the health care

provider or by patients themselves. Objective measures

used by the health care provider can include range of

motion, strength, endurance, structural measures ( radio­

graphs ) , proprioception, and joint laxity. Subjective mea­

sures, derived from patient-driven data, include general

health, pain perception, psychometric evaluations, disability

predictions, and overall patient satisfaction. Subjective

measurements have been found to be valid measurements

of outcome, and in many cases were more reliable than

the "objective" tests health care providers have relied on

for years. The most appropriate set of tools depends on

the question to be evaluated and the patient population;

usually a combination of these techniques is required .

Some common knee outcome measures include the

Short-Form 36 (SF-36), the Modified Lysholm Scale, the

Cincinnati Knee Rating Score, the Activities of Daily Living

Scale (ADL), the Knee Injury and OA Outcomes Score, the

Quality of Life Outcome Measure for Chronic ACL Defi­

ciency (ACL-QoL), and the International Knee Documen­

tation Committee ( IKDC) ( see volume 1 of this series,

Orthopedic Physical) .

Summary

Successful treatment and rehabilitation of ligamentous and

patellar tendon injuries of the knee require a fLill under­

standing of the anatomy and biomechanics of the knee.

Although imaging techniques continue to advance techno­

logically, the physical examination remains the most impor­

tant diagnostic tool. Each knee injury must be treated as an

individual and unique case; however, application of the

principles outlined in this chapter can lead to improved

outcomes over time.

References

To enhance this text and add value for the reader, all refer­

ences have been incorporated into a CD-ROM that is

provided witl1 this text. The reader can view the reference

source and access it online whenever possible. There are a

total of 3 1 5 references for this chapter.