MRI OF THE KNEEMARIA THERESA M. NAVARRO, MD Fourth Year Radiology Resident Department of Medical Imaging Quirino Memorial Medical Center

MRI OF THE KNEE

most frequently requested MRI joint study comprehensive examination of the knee road map for surgeons in arthroscopy or open surgery sensitivity & specificity of 90% to 95% for the menisci and close to 100% in cruciate ligaments

MRI OF THE KNEE

SAGITTAL IMAGES

meniscus cruciate ligaments T1W images, proton density, gradient echo sequences T2W image with fat suppression (cruciate ligaments, cartilage, and bones) collateral ligament cruciate ligaments

CORONAL PLANE

MRI OF THE KNEE

AXIAL PLANE

patellar cartilage trochlear cartilage medial patellar plica T2 sequences

ANATOMY OF THE KNEE

Anterior Supporting Structures: Quadriceps muscles Patellar tendon Medial Retinacular & Vastus Medialis Lateral Retinacular & Vastus Lateralis

Central Supporting Structures: ACL PCL

Medial Supporting Structures: Superficial MCL Deep MCL Joint capsule Medial Retinaculum

Lateral Supporting Structures: Illiotibial band Biceps femoris Lateral retinaculum LCL Joint capsule

Posteromedial Corner: Semimembranous Tendon Joint capsule Posterior Oblique Ligament

Posterior Supporting Structures: Posterior Capsule Gastrocnemius Muscles PCL

Posterolateral Corner: Popliteus Muscle & Tendon Arcuate ligament Joint capsule

By Hayes et al

MENISCAL TEARS

MENISCI

Functions

shock absorption stabilization lubrication proprioception

Normal Menisci

Medial meniscus

L a te ra l m e n iscu s

Meniscal TearGRADE 1 GRADE 2 GRADE 3

Abnormal Menisci According to Kaplan, et al., the only abnormal signal that has any real signficance is that which disrupts the articular surface of the meniscus tear Any signal that does not disrupt an articular surface intrasubstance or myxoid degeneration

Meniscal Tear

Abnormal morphology

Irregular margin of meniscus Focal defect on articular surface Abnormally small

Meniscal Tear

Vertical tear

Longitudinal tear Radial tear

Horizontal tear Complex tear

HORIZONTAL TEARhorizontal tear, cleavage tear, fishmouth tear meniscal tear that occurs in horizontal plane, dissecting through the circumferential collagen fibers Best Diagnostic Clue: linear horizontally oriented, increased signal intensity on short TE sequences

within meniscus from free edge Stoller et inward al.2004. Diagnostic Imaging: Orthopaedics

Horizontal Tear

Most Common Location: posterior horn of the medial meniscus

Stoller et al.2004. Diagnostic Imaging: Orthopaedics

Most common

Horizontal Tear

RADIAL TEAR

Vertical tear oriented perpendicular to the free edge of the meniscus

Best Diagnostic Clue GHOST MENISCUS when in plane of acquisition in root tears

includes root tear at meniscotibial attachement Location :

junction of the anterior horn and body of the lateral meniscus meniscotibial attachment posterior horn of the meniscus (root tear),

M e n i lR a d i lTe a r sca a

Absent bowtie sign Parrot beak tear Free-edge tear

Axial oblique graphic shows a radial tear involving the posterior horn of the lateral mensicus at the meniscotibial attachment

Sagittal PD FSE MR shows a radial tear of posterior horn of the medial meniscus at the root attachment giving a ghost meniscus appearance.

Radial Tear

MENISCAL CYST

Cyst extending from meniscal tear

horizontal tear most common

Best Diagnostic Clue : cystic mass extending from a meniscal tear Location :

anterior horn of the lateral meniscus posterior horn of the medial meniscus

Clinical Sign : Pisanis sign (palpable mass that disappears with flexion)

Sagittal FS PD FSE MR shows a moderate sized meniscal cyst projecting anteriorly from an anterior lateral Coronal PD FSE MR meniscus tear

shows a small meniscal cyst (arrow) adjacent to a lateral meniscal tear of the body

Meniscal Cyst

Fluid extrusion thru meniscal tear MR evaluation

Presence of cyst Presence or absence of

Meniscal TearSpecial types

Bucket-handle tear Flipped meniscus Inferior flap tear Meniscocapsular separation Meniscal root tear

BUCKET-HANDLE TEARVertical peripheral tear with displaced mesial portion to the notch of knee Best Diagnostic Clue:

coronal images show small meniscus body and meniscal fragments at the notch resulting in 2 meniscal fragments double posterior cruciate ligament (PCL) sign on sagittal images double delta sign

Bucket Handle Tear

MENISCAL FLAP TEARMeniscus oblique tear Tear of the meniscus with both longitudinal and radial components forming a flap of meniscal tissue that may become displaced Best Diagnostic Clue: obliquely oriented tear of the meniscus containing

longitudinal component radial component

Location : posterior horn and posterior aspect of body of medial

Meniscal Flap Tear

Vertical and horizontal component of a flap tear

Sagittal PD FSE MR shows a slightly displaced flap tear of the medial meniscus with characteristic vertical signal intensity involving the inner 3rd of the meniscus fibrocartilage

Flipped MeniscusToo much meniscal tissue Lateral meniscus

Inferior flap tear

Flap of meniscus

flip into medial gutter

Meniscal Root TearMedial meniscus posterior root Disruption of posterior horn near PCL

DISCOID MENISCUS Large congenitally dysplastic meniscus with loss of normal semilunar shape Result of failure of resorption of the central portion Best Diagnostic Clue : loss of normal semilunar shape filling lateral or medial compartment Location : lateral discoid meniscus is more commonDiagnostic Imaging: Orthopedics Stoller et al., 2004 than the medial

Discoid Meniscus

PitfallsM e n isco fe m o ra l lig a m e n t

Transverse ligament

Transverse Ligament

MRI OF KNEE LIGAMENTS

Li a m e n t i j ri s a re u su a l y g n u e l g ra d e d i te rm s o f th e i se ve ri : n r tyGrade I sprain some micro-tearing or slight stretching occurs, however the overall integrity of the ligament is preserved. The ligament hurts if stressed but is stable.

Li a m e n t i j ri s a re u su a l y g n u e l g ra d e d i te rm s o f th e i se ve ri : n r tyGrade II sprain partial disruption of the ligament. Painful to stress, there is detectable laxity but the ligament has an eventual endpoint.

Li a m e n t i j ri s a re u su a l y g n u e l g ra d e d i te rm s o f th e i se ve ri : n r tyGrade III tear complete ligament tear and laxity with no endpoint or stability to testing. As the nerves in the ligament are torn too, there is often minimal pain with stressing the joint

Direction of Injury-Producing Forces Acting on the KneeHyperextension Hyperextention, Varus Hyperextension, Valgus

Pure Varus

Pure Valgus

Flexion, Varus, Int. Rotation

Flexion, Anterior Tibial Translation

Flexion, Valgus, Ext. Rotation

By Hayes et al

Anterior Cruciate Ligament

Anterior Cruciate Ligament TearBest Diagnostic Clue : disruption of normal continuous low signal intensity ACL with irregularity and increased signal on T2WI Location : ACL in the intercondylar notch of knee most commonly caused

by forward translation of tibia, external rotation of the femur with respect to the tibia, valgus stress

Direct MR Signs of ACL Tear Discontinuity of fibers Abnormal slope of ACL Nonvisualization of the ACL fibers on both sagital and coronal planes Avulsion of the anterior tibial spine

Indirect MR Signs of ACL TearBone contusion sign: Lateral femoral condyle and posterior tibial plateau (pivotshift injury) Deep sulcus sign: Lateral femoral condyle Segond fracture: Capsular avulsion fracture of the lateral tibial plateau Kissing contusions: Anterior tibia and femur (hyperextension injury) Anterior drawer sign: Anterior translation of tibia relative to femur

Sagittal PD FSE MR shows the typical appearance of a proximal ACL tear

Coronal FS PD FSE MR shows an empty lateral intercondylar notch wall representing a grade III ACL tear

Associated bone contusions after an internal rotation valgus mechanism of injury involving the lateral femoral condyle and the posterolateral tibia

Sagittal FS PD FSE MR shows lateral bone injuries associated with an ACL tear including the posterolateral tibia and sulcus terminalis of the lateral femoral condyle. Proximal fibula is also injured.

Posterior Cruciate Ligament

PCL Teardisruption of the PCL usually after forced posterior displacement of the tibia Best Diagnostic Clue: discontinuous and/or thickened PCL fibers of increased signal intensity on all pulse sequences Location: Posterior tibia insertion site avulsion fracture Clinical : positive posterior drawer sign (excessive mobility of the tibia posteriorly) caused by direct trauma impacting the anterior knee in a posterior direction (dashboard injury with the knee in

PC L TEA R

Sagittal FS PD FSE MR shows a complete tear of the PCL

Sagittal FS PD FSE MR shows a complete tear of the PCL mid portion

PC L TEA R

Sagittal graphic shows the typical anterior bone contusion pattern of hypertension often seen with PCL tears

Sagittal STIR MR shows a partial PCL tear and an anterior subchondral contusion of tibia in a patient who suffered a dashboard injury

Contusion Patterns in PCL Tears

Direct Sign of PCL InjuryComplete tear Partial tear Peel-off injury: An avulsion injury of the femoral insertion of the ligament.

Indirect Signs of PCL InjuryBone marrow edema involving the anterior proximal tibia Avulsion of the posterior tibia at the PCL insertion site

LCL TEARfibular collateral ligament tear tear of the LCL after varus +/external rotation stress Best Diagnostic Clue: Discontinuous LCL fibers +/- thickening, hyperintense on FS PD FSE or T2WI Location: extends from lateral femoral condyle to insertion with the biceps femoris on the fibular head

usually at the proximal region

La te ra lC o l a te ra lLi a m e n t ( LC L ) Te a r l g

Tear at distal aspect of the lateral collateral ligament with mild retraction of the ligament proximally

Sagittal FS PD FSE MR shows a tear of the lateral collateral ligament

Sagittal PD FSE MR shows a normal LCL

Coronal PD FSE MR shows a normal LCL

La te ra lC o l a te ra lLi a m e n t Te a r l g

Coronal PD FSE MR shows a grade III sprain of the proximal aspect of the LCL

Sagittal FS PD FSE MR shows a mid and distal aspect LCL tear

Medial Collateral Ligament Teartibial collateral ligament tear secondary to valgus stress Best Diagnostic Clue: discontinuous MCL with thickening and increased signal intensity on all sequences within the ligament remnant Location : superficial and deep layers (medial capsular ligament)

superficial component medial (tibial) collateral ligament proper deep layer : meniscofemoral and meniscotibial attachments

M e d i lC o l a te ra lLi a m e n t Te a r a l g

Coronal oblique graphic shows a grade III tear of the proximal aspect of the medial collateral ligament

Coronal FS PD FSE shows a grade III MCL tear after valgus injury

Take Home PointMRI is a good imaging modality to detect the ligament injuries. Certain combination of forces cause specific injury patterns. Understanding the mechanism of injury is important to improve the diagnosis. Direct signs and Indirect signs are important for diagnosis of ligament injury.

Thank you po!