Clinical Imaging 37 (2013) 836–846

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Clinical Imaging

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Lower extremity overuse injuries in pediatric athletes: clinical presentation, imagingfindings, and treatment☆

Geraldine H. Chang a,⁎, David A. Paz a, Jerry R. Dwek b, Christine B. Chung c

a University of California San Diego Medical Center, Department of Radiology, 200 West Arbor Drive, San Diego, CA 92103b Rady Children’s Hospital of San Diegoc VA Medical Center San Diego

a b s t r a c ta r t i c l e i n f o

☆ Grants: None.⁎ Corresponding author. Tel.: +714 328 4717; fax: +

E-mail address: ghchang@ucsd.edu (G.H. Chang).

0899-7071/$ – see front matter © 2013 Elsevier Inc. Alhttp://dx.doi.org/10.1016/j.clinimag.2013.04.002

Article history:Received 15 March 2013Accepted 12 April 2013

Keywords:Pediatric overuse injuriesDevelopment of the physisPediatric musculoskeletal radiologyPediatric avulsion injuriesPediatric athletesOsteochondritis dissecans

Paralleling the growing popularity of organized sports among pediatric athletes, the stress and intensity oftraining regimens has escalated the frequency and severity of pediatric overuse injuries. It is essential thatradiologists have a thorough knowledge of the pathogenesis of these injuries and of their characteristicpatterns with different imaging techniques in order to appropriately diagnose overuse injuries in the pediatricskeleton. Knowledge of the classification, mechanism, clinical and imaging manifestations of acute andchronic overuse injuries of the lower extremities common among pediatric athletes can assist in imaging-based diagnosis and characterization of injury.

619 543 3746.

l rights reserved.

© 2013 Elsevier Inc. All rights reserved.

1. Introduction

Though historically, pediatric involvement in sports activities isusually recreational, recently the trend has shifted from a leisure-likequality to one of training and preparing for a more intensive career insports [1]. Pediatric athletes must endure more frequent and intensetraining regimens, resulting in an increase in overuse injuries.Approximately 1.5% of pediatric recreational athletes undergo sometype of injury [1,2]. This primarily affects males between the ages of10-14 years [3]. The pediatric population is more prone to overuseinjuries involving the physes and apophyses due to inherentweaknesses in the immature skeleton [4,5]. [The physis is the weakestlink in the pediatric skeleton; ligamentous structures are 2-5 timesstronger than the physis] [3–5].

In the setting of traumatic injury, onemust consider both the acuteinjury allowing for a facile clinical and imaging diagnosis as well aschronic repetitive micro trauma, which can be more challenging toevaluate. Exposure to repetitive stress can lead to a chronic overuseinjury without an acute event. However, with accurate incorporationof patient information including age, clinical history, physicalexamination findings and his or her primary sport, imaging cangenerally result in an accurate diagnosis. As the mechanism of injurycan vary by sport, it is evident that clinical history is crucial to theradiologist in order to deploy effective imaging [2,3,6].

In this article, we discuss and illustrate the radiographic, computedtomographic (CT), and magnetic resonance imaging (MRI) appear-ance of a variety of acute and chronic overuse injuries of the lowerextremities including the back, pelvis, knee and ankle and foot aslisted in Table 1 in addition to the clinical presentation and treatmentof these various disease entities.

Interpretation of the radiographic imaging of pediatric overuseinjuries requires a comprehensive knowledge of the physis, which isalso known as the cartilaginous growth plate. The physis consists of acolumnar arrangement of chondrocytes within a thin matrix ofproteoglycan aggregates [4,5]. At puberty, physes throughout thebody undergo gradual closure. Until full closure, it is susceptible toinsults that can lead to permanent and debilitating injury [1,4,7–9].

2. Back & spinal injuries

Back pain in pediatric athletes is often difficult to diagnose andtreat. Factors such as growth spurt, abrupt increases in trainingintensity and leg-length inequality are predispositions for backinjuries unique to the pediatric population. Two common backinjuries seen across multiple sports will be discussed: pars inter-articularis stress fracture and sacral stress fractures.

2.1. Pars Interarticularis stress fracture in contact sports

Spondylolysis is a fracture of the pars interarticularis, the weakestpart of the vertebra [10] and spondylolisthesis involves movement ofone vertebral body on an adjacent one in the coronal plane. Both

Table 1Lower extremity overuse injuries in pediatric athletes

Anatomic location Type or description of injury

Back & Spine Pars interarticularis stress fractureSacral stress fractures

Pelvis & Hip Avulsions of:• Anterior Superior Iliac Spine (ASIS)• Anterior inferior iliac spine (AIIS)• Ischial tuberosity• Lesser trochanter• Iliac crestRectus femoris tear

Knee Chronic physeal stress injuryTibial tuberosity avulsionOsteochondritis dessicans (OCD)Osgood –Schlatter diseaseSinding-Larsen-Johansson syndromePatellofemoral syndrome (PFPS)

Lower Leg Medial tibial stress fractureAnkle/Foot OCD of the talus

Sever’s Disease

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conditions are the result of repetitive hyperextension and continuedstress. Prevalence of spondylolysis is low in young children, increasingwith age. The typical patient presenting with spondylolysis is aCaucasian, athletically active boy [10]. It is associated with manyactivities including contact sports such as football, soccer, hockey andlacrosse, as well as sports that cause overloading of the posterior archof the vertebra through hyperextension, such as gymnastics andtennis [10,11]. Athletes involved in contact and diving sports are atincreased risk of low back pain due to spondylolysis or spondylolisth-esis. Patients often present with low back pain that may radiate to oneor both buttocks that is exacerbated by lumbosacral twisting andhyperextension [12]. Physical examination may reveal tendernessover the paraspinous region in the injured area and pain with singleleg extension.

Radiography of the lumbosacral spine, performed in the obliqueand lateral planes [Fig. 1 A] can demonstrate the pars interarticularisdefect and the degree of spondylolisthesis, respectively. However, thedefect is frequently not visible on plain radiography, necessitatingother imaging modalities for diagnosis [13]. CT [Fig. 1 B] is verysensitive in identifying the presence of a fracture. The parsinterarticularis is a ring made up of the posterior aspect of thevertebral wall, medial walls of the pedicle, anteromedial parsinterarticularis, lamina and anterior portion of the spinous process.In the case of a fracture, on axial views, CT findings can includeinterruption of pars interarticularis on both sides, appearing as anincomplete ring [10]. An intact ring essentially rules out the presenceof spondylolysis. However, close examination and thin sections arenecessary to rule out an incomplete fracture [10] Stress change can beidentified on CT as abnormal sclerosis at the level of the parsinterarticularis in many cases extending into the pedicle proper.Though not very sensitive in identification of a fracture and itscharacterization, nuclear scintigraphy is very useful at the diagnosis ofstress changes and for excluding this condition for an adolescentathlete presenting with minimal back pain [10].

MRI [Fig. 2] has been shown to diagnose both bilateral andunilateral lumbar spondylolysis. Acute injuries can yield variable T1and T2 signal intensities consistent with marrow edema, as well asfracture line identification. Specifically, in a unilateral defect, MRImay demonstrate indirect signs such as reactive sclerosis of thecontralateral pedicle, asymmetric posterior neural arches, wideningof the interspinous distance, widening of the spinal canal withanterolisthesis or posterior subluxation of the posterior element,marrow changes of the pars interarticularis defect, and degenerativechanges of the facet joints and disks adjacent to the affected vertebradefect of the pars interarticularis [14]. These indirect signs may varydepending on the affected lumbar level due to differences in axial

loading and lordosis [14]. Recent studies suggest that MRI should beused as first-line examination for suspected pars interarticularisfracture as the goal of imaging is to not only detect the fracture butalso to detect stress changes before the presence of a fracture. MRI ismore sensitive and specific in comparison to bone scintigraphy or CTscan in detecting both fracture and stress changes [14]. In addition,MRI is the most accurate in demonstrating the normal parsinterarticularis, acute complete defects and chronic establisheddefects [13]. CT should be used only for acute defects as a baselinefor follow-up and for supplementary evaluation of indeterminatecases [13].

If a fracture is present, initial treatment involves restriction ofactivities. In young athletes with an acute onset of complaints, thefracture has the potential to heal. Use of a back brace is indicated untilpain has resolved [12,15]. Healing can be followed with bone scansuntil the intensity of the uptake diminishes [12,15]. In chronic cases,treatment is symptomatic with anti-inflammatory medications,bracing, and physical therapy with return to activity when thesymptoms have subsided [12,15].

2.2. Pars Interarticularis stress fracture in gymnasts

The most common site of complaints for gymnasts is the lowerback, the so-called “gymnast back” [16]. Lumbar spine injuries arecommon in gymnastics because of the repetitive hyperextension andexcessive training. Initial complaints may be attributed to muscularstrains, but persistent pain is frequently caused by stress fractures ofthe pars interarticularis [16,17].

Gymnasts can present with radiographic findings consistent withspondylolysis. MRI can also depict this injury in addition to discdegeneration, which often accompanies spondylolysis in gymnasts.This can be evidenced as loss of disc height, decreased signal intensityfrom the nucleus pulposus and posterior disc bulging [16–18].

Treatment includes optimizing the level of conditioning of theback extensors and abdominal muscles and ensuring proper perfor-mance of technique. Limits on the number of extension elements in agiven routine and immediate discontinuation of extension if paindevelops can prevent more severe injuries [16].

2.3. Sacral stress fractures

Sacral stress fractures in athletes are rare but important torecognize since they can mimic disk disease [19]. Sacral stressfractures occur almost exclusively in individuals participating inhigh-level running sports, such as track or marathon and mostcommonly appear after increase in intensity of training or changeswith current training such as new shoes or running surfaces [12,20].The etiology of these fractures is believed to be due to concentration ofstress in the sacrum as vertical body forces are repetitively transferredfrom the sacrum to the spine [21]. Patients often present with lowback and vague buttock pain or with sacral pain radiating into thebuttock. Physical examination is often unreliable as many patientspresent with diffuse pain in the low back, sacral and buttock region,necessitating radiographic imaging [19].

X-rays are helpful in excluding tumors but stress fractures areoften missed due to overlying bowel gas, geometry of the sacrum andlack of visualization, as these fractures do not produce callus [19]. CTand MRI findings are diagnostic as the linear appearance on eitherimaging technique is consistent with a fracture. Other findings includelinear sclerosis with cortical disruption on CT and linear abnormalsignal intensity paralleling the sacroiliac joint on MR [19,22].

Treatment includes a brief period of limited weight bearingfollowed by progressive mobilization and physical therapy withreturn to sports in one to two months after resolution of pain [12,23].

Fig. 1. Pars interarticularis stress fracture. Lateral radiograph (A) demonstrates the defect in the L5 pars interarticularis (yellow arrow) and sagittal CT (B) image demonstrate thedefect in the L3 pars interarticularis (white arrow) in a 16 year old male presenting with lower back pain.

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3. Pelvis and hip

Injury to the pelvis often involves avulsion injuries that are oftenseen in sports such as soccer, rugby, ice hockey, gymnastics and

Fig. 2. Pars interarticularis stress fracture. Sagittal T2 FS image shows the defect in theL5 pars interarticularis (yellow arrow) as well as marrow edema and stress changes atthe L4 level (white arrow)in a 20-year-old male football player.

sprinting. These sports involve kicking, rapid acceleration, decelera-tion and jumping that can lead to sudden, violent or unbalancedmuscle contraction that result in hip or pelvic avulsions [6,9]. In itsmost typical presentation, a sudden sharp pain or pop during amuscular contraction is followed by limping or inability to bearweight along with restricted active motion and weakness [9,24].Avulsion injuries can occur anywhere on the pelvis where there ismuscle to bone attachment [9,24,25]. Of note, all avulsion injuries canalso be due to acute trauma without history of chronic overuse. 5types of avulsion injuries to the pelvis will be discussed: anteriorsuperior iliac spine (ASIS), anterior inferior iliac spine (AIIS), lessertrochanter and ischial tuberosity and iliac crest. Although not anosseous pelvic injury, tear of the rectus femoris muscle is commonlyassociated with pelvic injuries and will also be discussed.

In many cases, the distinction between an acute avulsive injuryand a chronic avulsive change is blurred. Many acute avulsions occuras a result of an acute stress on a chronically weakened and damagedapophyseal physis.

3.1. Anterior superior iliac spine (ASIS) avulsion

In an acute ASIS avulsion, the muscle involved is the sartorius andtensor fascia lata (TFL). Acute avulsion from the ASIS is due to aforceful contraction of the sartorius muscle when the hip is extendedand knee is flexed. This injury is most commonly seen as a result offootball accidents, but has also been reported with sprinting, bicycleracing, softball injuries and track [25]. In 90% of cases, a palpable massis felt with pain below the anterior iliac crest [6].

Unlike an acute avulsion [Fig. 3 A], a chronic ASIS avulsion [Fig. 3 B]can yield irregular callus formation during healing about the ilium,mimicking a neoplasm [6,9]. In such cases, CT may be helpful indiagnosis. Another pitfall in the diagnosis of an ASIS avulsion is themisdiagnosis of a TFL avulsion as an ASIS avulsion [6]. Avulsion of thesartorius is smaller, displaced anteriorly and seen in sprinting [26]. ATFL avulsion is larger and displaced laterally [26].

Fig. 3. ASIS avulsion. AP radiographs demonstrate an acute right ASIS avulsion (A, yellow arrow) and a chronic ASIS avulsion (B, white arrow), which demonstrate an irregular callussecondary to healing, mimicking a neoplasm.

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Conservative management consisting of rest usually follows anASIS avulsion. In more severe cases, splinting of the knee in flexion isdone to reduce traction of the avulsed fragment.

3.2. Anterior inferior iliac spine (AIIS) avulsion

Avulsion of the AIIS is less common than ASIS. The straight head ofthe rectus femoris muscle attaches to the AIIS and the avulsionfracture from the AIIS can occur from forceful hip extension with kneeflexion in activities such as kicking a ball (soccer), jumping fromstarting blocks and maintaining muscle [6,8,9].

On radiography [Fig. 4], an acute AIIS avulsion appears as a bonyexcrescenceemanatingfromtheiliumwithirregularityorproliferationofthe underlying bone. Similar to an ASIS avulsion, a chronic AIIS avulsionmay simulate a malignant lesion in its healing phase due to myositisossificans and in such cases especially when only a remote history ofminor trauma exists, CT orMRImay be helpful in diagnosis [8,9,11].

Similar to avulsion fractures from the ASIS, AIIS avulsion fracturesare treated with conservative management consisting of rest. Surgicalintervention is only indicated if displacement ismore than 2 cm, in thecase of a nonunion or if there are clinical symptoms secondary to bonyprotuberance formation secondary to healing [8,9,27].

3.3. Tear of rectus femoris muscle

Tearing of the rectus femoris muscle is included as a pelvic injuryas the rectus femoris is attached to the acetabulum and the AIIS and

Fig. 4. AIIS avulsion. AP radiograph demonstrates a right. AIIS avulsion (arrow),appearing as a bony excrescence detached from the ilium.

functions in hip flexion and knee extension. This is a commonpediatric injury that can usually occur due to an explosive kick orcontraction in sports such as long jump or soccer [28,29]. Athletes canmask a tear by recruiting the remaining quadriceps muscles but canno longer attain pre-injurymaximal efforts. The rectus femoris muscleis the quadriceps muscle most prone to injury due to its length as itspans two joints (hip and knee). It is prone to direct trauma as welldue to its superficial and anterior location [29].

The extensor apparatus of the lower extremity is a long complexstructure and overuse injuries at multiple levels may coexist so thatradiographs in athletes with rectus femoris muscle tears frequentlyreveal chronic avulsive changes at the AIIS. On MRI, a rectus femorismuscle tear appears as a high T2 signal on MRI [29]. In addition, therectus femoris muscle layer will appear edematous and discontinuousand if the tear is complete, retraction of the torn ends can also be seenon MRI [30].

Early diagnosis is crucial to prevent proximal contraction andscarring of muscle and to allow for surgical intervention in the case ofa complete tear [28,29].

Fig. 5. Ischial tubersity avulsion. Coronal T2 FS image demonstrate displacement of theischial apophysis (arrow) due to a hamstring avulsion in a 10-year-old femalepresenting with pain in the buttock region.

Fig. 7. Iliac Crest avulsion. Axial CT image (A) demonstrate avulsion of the left iliaccrest (arrow) and axial T2 FS image (B) demonstrates an iliac crest avulsion

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3.4. Ischial tuberosity avulsion

Ischial tuberosity avulsion is the most common site of pelvic andhip avulsions. It is seen in sports such as soccer, water-skiing, dancing,weight lifting, gymnastics and ice-skating, which all involve suddenbursts of speed that causes extreme active contraction of thehamstrings and adductor muscles of the thigh. Patients usuallyexperience a popping or tearing sensation and present with pain inthe buttock region, an antalgic gait, or inability to walk [6].

A pelvic radiograph will reveal a fragment inferior and lateral tothe ischial tuberosity indicating the diagnosis of avulsion of ischialtuberosity [31]. On MRI [Fig. 5], typical findings include displacementof the ischial apophysis inferiorly and laterally with the hamstringtendons. Frequently tendon or muscle tear is present [31]. In addition,MRI allows comparison of the displacement of the ischial apophysison the injured side to the uninjured side. Note that findings arefrequently bilateral although the patient may not be aware of acontralateral injury. CT can reveal similar findings, as well asheterotrophic bone formation areas in surrounding muscle tissue[31]. Follow-up x-rays, 6 months after injury, can show excessivebony formation, mimicking osteomyelitis or neoplasm and hetero-trophic ossification areas in surrounding peripheral tissues [31]. Thus,CT may be useful for chronic cases and for their follow-up becausechronic avulsion fractures frequently result in prominent boneformation and CT is often the best imaging modality for bonystructures [6,32,33].

Patients with ischial tuberosity avulsions respond well toconservative treatment if displacement caused by the avulsion isless than 2cm. However, a displacement of more than 2 cm can lead toa fibrous union and can result in extended disability [6].

with mild physeal widening and edema within the iliac crest and the adjacentmusculature (circle).

3.5. Lesser trochanter avulsion

Avulsions of the lesser trochanter may occur in young athletes dueto sudden contraction of the iliopsoas muscles but it is a rare overusepediatric injury. Injury has been reported in running, football andbasketball injuries [11]. Clinically, the patient presents with consid-erably painful flexion with decreased function and tenderness in themedial aspect of the hip [9,34].

X-ray [Fig. 6] is sufficient for diagnosis and separation anddisplacement of the lesser trochanter can be seen [35]. These imagingfeature are more apparent on CT. MRI can also show the presence ofthe avulsion in addition to stress changes.

In comparison to adult patients where there would be concern forunderlying osseous malignancy, pediatric lesser trochanter avulsions

Fig. 6. Lesser trochanter avulsion. AP radiograph demonstrate separation anddisplacement of the right lesser trochanter (arrow).

are more likely to be of benign etiology and respond well toconservative treatment [34].

3.6. Iliac crest avulsion

The least common site for a pelvic avulsion is the iliac crest. Theacute form of this injury occurs as a result of the forceful traction ofexternal and internal oblique and transverse abdominal musclesduring abrupt changes in running direction or repetitive microtraumain long-distance runners [9,32] or from swinging a bat, which resultsin an avulsion of the anterior aspect of the iliac crest at the origin ofthe tensor fascia lata [26]. On examination, symptoms are reproducedwith resisted abduction of the ipsilateral side and palpation of theiliac crest.

Radiography or CT [Fig. 7 A] will demonstrate asymmetry of theiliac crest apophyses [9]. Oblique radiographs will reveal an avulsionof the iliac crest. MRI [Fig. 7 B] findings includemild physeal widening,varying degrees of bone edema within the iliac crest, edema withinthe adjacent musculature [36].

Conservative treatment of 4-12 weeks of physical therapy thatinclude activity modification to avoid running, strength training ofcore postural muscles and flexibility training for the iliopsoas,hamstring and hip adductor and abductor muscles is usuallysuccessful with excellent prognosis [6,36].

4. Knee

The knee is a common site for pediatric overuse injuries, rangingfrom common overuse injuries found in all athletes to specific age-related injuries of the ossification centers in the knee joint [37,38]. Sixtypes of pediatric knee injury will be discussed here: chronic physealstress injury, tibial tuberosity avulsion, osteochondritis dessicans

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(OCD), Osgood-Schlatter disease, Sinding-Larsen-Johansson syn-drome and patellofemoral pain syndrome (PFPS).

4.1. Chronic physeal stress injury

Unlike Salter-Harris (SH) fractures, which are usually due to acutetrauma, chronic repetitive microtrauma can also cause physeal stresschanges prior to its closure in the teenage years. Metaphyseal andepiphyseal vessels supply the physis with nutrients needed forcalcification of the matrix and eventual transition of cartilage tobone. Without normal metaphyseal blood flow, this process isdisrupted and long columns of hypertrophic cartilage cells from thephysis extend into the metaphysis, leading to the physeal widening ofthe knee [39]. The path of a physeal injury is complex and frequentlyinvolves the epiphyseal sided vessels. Damage to these vessels affectsthe resting or germinal zone of the physis, which provides a readystock of chondrocytes for the physis. Loss of these cells causes slowingor cessation of growth followed by physeal bridging [39].

Physeal widening can be seen on radiographic imaging but is moreeasily detected on MRI [Fig. 8] as this disease process produces acartilage signal intensity of apparent physeal widening [39]. Further-more, MRI may be indicated to exclude other injuries that may causeprolonged joint pain. These areas of physeal widening differ fromSalter-Harris type 1 injuries in that no discrete fracture is identifiedthrough the cartilage; the widening can be focal and neitherepiphyseal nor apophyseal displacement is seen [39,40].

With strict rest, healing occurs and normal endochondral growthresumes. Conservative treatment includes rest immobilization andimprovement can be monitored both by symptoms and imaging withresolution often within 3 months. It is important to recognize physealwidening as children should not undergo physical therapy andprogressive rehabilitation such as in cases with patients with overuseknee pain [39,41] It is important for the child to discontinue the

Fig. 8. Chronic physeal stress injury. Sagittal T2 FS image demonstrates a cartilagesignal intensity (arrows) of apparent physeal widening.

offending sport and rest to allow rapid healing as noncompliance mayresult in subsequent malalignment [39,42].

4.2. Tibial tuberosity avulsion

Avulsion of the tibial tuberosity is associated with sports activitiesthat require jumping. The unique nature of the tibial tuberosityexplains the etiology of these injuries. The tibial tuberosity is anextension of the proximal tibial physis, which is initially composed ofepiphyseal cartilage and with maturation, the ossification centerconverts fibrocartilage to the weaker columnar cartilage. Thismaturation coupled with a history of overuse can increase thepropensity for avulsion [43–45]. These injuries are most common inthe 12-16 year old age group and often occur with violent activeextension of the knee or passive flexion against the contractedquadriceps muscles [6,44,45]. Clinically, patients present withswelling, pain, tenderness over tuberosity and often hold the kneein flexion due to inability to extend.

Radiography [Fig. 9] is often sufficient for diagnosis. The imagingmodality of choice is plain radiography with oblique views of theproximal tibia as the tubercle lies lateral to the midline [38]. Plainradiograph will show displacement of the tubercle in the case whereoveruse stress changes weaken the physis and result in a completeavulsion.MRIwill show the avulsed fragment aswellwith high-signal-intensity edema at the fracture site and in surrounding soft issues [38].

Treatment involves immobilization for non-displaced fracturesand fixation for displaced fractures [45].

4.3. Osteochrondritis dissecans (OCD) of the knee

Osteochrondritis dissecans (OCD) is theorized to be due to injuryto an ossification center in the epiphyseal cartilage [46,47]. The causeof OCD is often unknown and theories include growth disturbances,and mild recurrent injuries leading to reduction in blood flow to thefocal subchondral bone [46,47]. The knee is the most commonly

Fig. 9. Tibial tuberosity avulsion. Oblique lateral radiograph demonstrates displace-ment of the right tibial tuberosity (arrow).

Fig. 10. Osgood-Schlatter Disease. Lateral radiograph shows fragmentation at the tibialtubercle (arrow) in a 12-year-old male with clinical symptoms indicative of Osgood-Schlatter Disease.

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affected joint and 80% of OCD cases of the knee are present at theposterolateral corner of the medial femoral condyle with 75%unilaterality [46,47]. Patellar OCD is not uncommon. Prevalence istwice as high in males and patients are typically under the age of 18[46]. Patients are often asymptomatic if the osteochondral defect doesnot displace. If symptomatic, patients have vague pain symptoms andoften complain of a buckling sensation. Skeletally immature patientscarry a better prognosis.

Radiographically, OCD initially presents as an irregularity in theossifying margin of the epiphysis. Later radiographs reveal a flake ofbone, which grows at the same rate of the epiphysis yet remainsseparated from it by a linear lucency [48,49]. This sclerotic centralbony focus is usually several millimeters thick and has the generalappearance of an ununited fracture [49,50]. While radiographs candepict OCD well, they are not very helpful in the determination of thestability of OCD lesions. MRI has been identified as a useful means fordiagnosis and characterization. MRI can provide information regard-ing the size and location of the lesion as well as the degree of healingbetween the osteochondral fragment and the donor site. MRI is usefulfor detecting instability of OCD as well as identifying cartilage,fractures, focal defects caused by displaced fragments and underlyingcysts [51]. Use of MRI for detecting fragment instability requiresknowledge of revised criteria for OCD instability based on skeletalmaturity, differentiating between juvenile and adult OCD lesions [51].The presence of a high T2 signal intensity rim, a high T2 signalintensity fracture line extending through the articular cartilage, or afluid-filled osteochondral defect is an unequivocal sign of instability inpatients with adult OCD of the knee [51]. However, the presence of ahigh T2 signal intensity rim or the presence of cysts surrounding anOCD lesion is nonspecific in patients with juvenile OCD of the knee[51]. In juvenile OCD, the presence of multiple cysts and the presenceof a single cyst greater than 5 mm in diameter both have a lowsensitivity but high specificity [51]. A high T2 signal intensity rimsurrounding a juvenile OCD lesion indicates instability only if it hasthe same signal intensity as adjacent joint fluid, is surrounded by asecond outer rim of low T2 signal intensity or is accompanied bymultiple breaks in the subchondral bone plate on T2-weighted MRimages [51]. These secondary MRI findings yields 100% sensitivity and100% specificity for detection of unstable juvenile OCD lesionssurrounded by a high T2 signal intensity rim [51].

Treatment of OCD is usually conservative as lesions are typicallystable and those with an intact articular surface have loading goodprognosis. Nonarticular sided drilling is frequently used to encourageblood flow and initiate healing in the OCD. With this technique, a drillbit is inserted into the bony epiphysis either medially or laterally andis advanced into the lesion. In this way, the intact articular surfaceremains undisturbed. In cases where imaging shows injury to theoverlying articular cartilage, arthroscopy is used to examine moreclosely the articular cartilage and if not intact, articular sided drillingmay be used to promote healing before the lesion progresses [52]. Insome cases, bone grafting or cartilage allograft is indicated and in thecases of large lesions, surgical excision is necessary [52].

4.4. Osgood-Schlatter disease

Osgood-Schlatter is a pediatric disease most often seen in 10-15year old males [6,53]. The etiology of Osgood-Schlatter disease isrepetitive microtrauma causing a traction apophysitis of the tibialtuberosity and associated distal patellar tendonitis [6,53]. Thus,Osgood-Schlatter disease is a chronic avulsion injury. It is mostoften associated with sports involving jumping, squatting and kicking.Diagnosis is usually made clinically when a patient presents withswelling, pain and tenderness to palpation over the tibial tuberosity.Patients can also develop a visible tender bump due to the reactivesecondary heterotopic bone formation at insertion of patellar tendon.[53–55] It is bilateral in 20-50% of the cases [56–58].

Radiography [Fig. 10] shows fragmentation and irregular ossifica-tion at the tibial tubercles, calcification and thickening of patellartendon, and overlying soft tissue swelling [54]. However, theseradiographic findings are not always present in all patients withsymptoms of Osgood-Schlatter. Thus, MRI [Fig. 11] findings of softtissue swelling anterior to the tibial tuberosity, loss of the sharpinferior angle of the infrapatellar fat pad and surrounding soft tissue,thickening and edema of the inferior patellar tendon and/orinfrapatellar bursitis are the most important diagnostic criteria forOsgood-Schlatter disease [54,55].

Treatment of Osgood-Schlatter disease is conservative includinguse of ice, analgesic and nonsteroidal anti-inflammatory drugs, use ofa knee immobilizer if necessary and informing the patient to avoidpain-producing activities. Once acute symptoms have abated, physicaltherapy including quadriceps-stretching and hamstrings-stretchingcan be done.

4.5. Sinding-Larsen-Johansson syndrome

Sinding-Larsen-Johansson syndrome is also a disease secondary torepetitive microtrauma and is also known as patellar tendonitis or so-called “jumper’s knee”. In this condition, chronic repetitive traction isdirected at the proximal attachment of the patellar tendon in theinferior pole of the patella. The etiology appears to be tractiontendinitis with de novo calcification in the proximal attachment ofpatellar tendon [59]. This condition is most common amongprepubescent athlete in the 10-13 year age group and often associatedwith running, jumping and kicking sports [60]. Patients often presentwith localized tenderness at the lower pole of the patella and anotherwise normal examination [60].

On plain radiography, calcification or ossification of the patellartendon can be demonstrated [38,59]. MRI [Figs. 11 & 12] findingsinclude fragmentation of lower pole of patella, marrow edema withinthe fragments, thickening of patellar tendon at its insertion and

Fig. 11. Osgood-Schlatter Diseas & Sinding-Larsen-Johanssen Disease. Sagital PD and PD FS images demonstrate edema of the inferior patella tendon suggestive of Osgood-SchlatterDisease (yellow arrows) and fragmentation of the lower pole of the patella suggestion of Sinding-Larsen-Johanssen Disease (white arrows).

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edema of Hoffa’s fat pad. Ultrasound imaging is also effective and canbe used for periodic follow-up during the course of this condition butMRI allows one to rule out other intra-articular derangements [61,62].

Treatment is often conservative, requiring rest from training andrehabilitation involving extensor mechanism stretching. The condi-tion can last from three to twelve months [59]. Surgery is reservedonly for refractory cases and involves excision of the affected area ofthe tendon [38].

4.6. Patellofemoral pain syndrome (PFPS)

Patellofemoral pain syndrome (PFPS) is one of the most frequentcomplaints among adolescent, female athletes. Patients often presentwith an insidious onset of chronic anterior knee pain not associatedwith acute trauma or injury. Physical examination is often normal andnot associated with any mechanical symptoms such as clicking,locking or instability [60]. Pain is exacerbated by activities thatincrease loading across the patellofemoral joint, including jumping,climbing stairs and sitting for long periods of times [60].

Radiographic imaging should include multiple views includingweight-bearing anterior-posterior, weight-bearing lateral, axial viewwith 20-45 degrees of knee flexion. Axial view can show abnormal-ities of lateral patellar displacement, lateral patellar tilt and dysplasiaof the trochlea [63]. However, radiographic findings can be found inboth asymptomatic and symptomatic patients and thus, imagingfindings in combination with physical examinations are oftennecessary to tailor appropriate treatment [63]. CT and MRI are oftennot necessary for PFPS but can be helpful if PFPS is presenting witharticular injuries such as chondromalacia patellae, patellar stressfractures and loose bodies [63,64]. MRI is also useful to track theabnormalities of alignment associated with PFPS. Tracking refers todynamic patellofemoral alignment during knee motion. PFPS is anexample of an imbalance of the forces on the patella that produceabnormalities of alignment and tracking [63]. Patellar tracking is bestexamined with the knee in 5-30 degrees of flexion as beyond that the

patella centralizes in the trochlear groovewith increasing flexion [63].PFPS can also present with lateral patella dislocation, which is usuallyasymptomatic and MRI findings are sometimes the first indication ofthe diagnosis [63]. Findings can include joint effusions, injuries to themedical retinaculum, signal changes in the superior portion of Hoffa’sfat pad, contusion of the anterolateral. PFPS can also present withexcessive lateral pressure syndrome, which is a condition in whichlateral patellar tilt is dominant with little or no subluxation [63]. MRIfindings will reveal cartilage loss, sclerosis and cystic change of thelateral patella and trochlea [63].

Treatment of PFPS includes physical therapy to strengthen thequadriceps and lower extremity flexibility in addition to bracing andorthotics, especially in patients with excessive foot pronation [60]. Inthe case where MRI reveals damage to the medial patellofemoralligament (MPFL), surgery is advocated to prevent recurrent patello-femoral instability and dislocation [63].

5. Lower leg

5.1. Medial tibial stress syndrome

Medial tibial stress syndrome is most commonly seen in runners,with a female preponderance [65,66]. Clinically, the patient mostcommonly presents with a focal tenderness in the middle to distaltibia [65].

Plain radiography is often normal with sensitivity as low as 15%.Furthermore, radiographic evidence of a stress fracture can beambiguous if symptoms have persisted for less than 3 weeks andeven after 3 weeks, a fracture line may not be seen on plainradiograph. However several options exist for advanced imagingdiagnosis. CT provides excellent diagnostic potential but carries aradiation dose, which must be considered in a pediatric patient. A 3-phase bone scan is also very sensitive as it reflects osteoblasticactivity, as the body attempts to repair the fracture. Within the firstfew days after a fracture, a bone scanmay be negative. 95% of scans are

Fig. 12. Sinding-Larsen-Johanssen Disease. Sagittal T2 FS image demonstratefragmentation of lower pole of patella (arrow) and edema of Hoffa’s fat pad.

Fig. 13. Severs disease. Lateral radiograph demonstrates sclerosis and fragmentation(arrow) of the calcaneal apophysis in a 6-year-old boy. While this can be the normalappearance of the calcaneal apophysis, the patient was symptomatic and improvedwith rest.

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positive within 24 hours and almost 100% are positivewithin 72 hours[30]. However, radiation exposure remains concerning. In addition, aneoplasm or infection may appear identical to a stress fracture onbone scan and thus, a thorough clinical history is essential. MRI is alsovery sensitive and preferred over bone scan due to the lack ofradiation dose and its ability to distinguish from other entities as well.MRI can show an irregular horizontal band of low signal intensitysurrounded by periosteal or endosteal marrow edema typical of stressfractures [67,68]. On follow-up, radiograph can demonstrate faintradiolucent striations in the anterior tibial cortex and bone scan canshow residual increased uptake [68,69].

Treatment is nonoperative and includes primarily reduction inrunning and activity restriction until healing is seen, possibly up to 6months [30].

6. Ankle & foot

Two overuse injuries in the pediatric ankle and foot will bediscussed: Osteochondritis Dissecans (OCD) of the talus andSever’s disease.

6.1. Osteochondritis Dissecans (OCD) of the talus

Talar OCD is similar to the OCD findings in other locations. Patientsoften present with chronic ankle pain with a history of intermittentswelling and weakness [70,71]. The mechanism of injury is aninversion injury of the ankle. In a posteromedial lesion, a plantar-flexed ankle is forced into inversion and external rotation, causingimpaction of the posteromedial talus onto the tibia [71,72]. Aposteromedial lesion can be secondary to trauma or due to overuse,causing a deep lesion with a cup shape [72]. In an anterolateral lesion,a dorsiflexed ankle is forced into inversion, causing impaction of taluson the fibula [71,72]. Unlike a posteromedial lesion, this is often ashallow lesion [72].

Radiographically, the appearance of talar OCD is similar to theappearance at the knee and thus, can be diagnosed by a shallowlucency sometimes with a sclerotic central bony focus at the articularsurface. A curvilinear lucency separates the fragment from the donorsite, which in turn may be rimmed with sclerosis. Here again, whileradiography may depict the existence of the OCD lesion, it is not

sensitive for the determination of instability. As used in the knee,MRI can provide information regarding the size and location of thelesion as well as the degree of healing between the osteochondralfragment and the donor site. As seen in the knee, fluid hyperintensityalong the donor site margin with breach of articular cartilage mayindicate instability.

Treatment is similar to that used in the knee with nonarticular sideddrilling used for lesionswith intact articular cartilage and articular sideddrilling for thosewith disrupted articular cartilage [51,52,73].

6.2. Sever’s disease

Sever’s disease (calcaneal apophysitis) is another overuse injurydue to chronic, repetitive microtrauma, which is theorized but notproven to be due to rapid growth spurts. Traction from thegastrocnemius-soleus complex can lead to apophysitis of thesecondary ossification center of the calcaneus, resulting in inflamma-tion at the site at which the Achilles tendon attaches to the heel [60].This condition is more common among boys, seen mostly in the 9-12year age group and associated with young athletes participating inimpact sports especially those that involve running [60]. The classicalphysical examination finding is pain reproduced with medial andlateral compression of the heel [60].

Sever’s disease is generally a clinical diagnosis and conventionalradiographs [Fig. 13] are used to exclude other possible causes of heelpain such as a stress fracture, infection of neoplasm. Radiographicfindings indicative of Sever’s disease include sclerosis and fragmen-tation [74]. However, these findings can also be observed in normalchildren. Recent studies have also shown that ultrasound findings canalso be used for diagnosis and demonstrate the fragmentation ofsecondary nucleus of ossification of the calcaneus and surroundingsoft tissues [74]. Ultrasound might also be favored to preventexcessive radiation. CT or MRI are not often used for initial diagnosisfor Sever’s disease but is useful to exclude osteomyelitis or fusion ofthe small bones of the hindfoot. However neither is necessarilyrequired [74,75]. MRI will demonstrate edema in the fatty marrow ofthe apophysis and in severe cases the adjacent body of calcaneus andheel pad [75,76]. A MRI [Fig. 14] can be useful to rule out a calcanealstress fracture, which presents as bone bruising and edema in thecalcaneal metaphysis as well as the apophysis.

Treatment for Sever’s disease is conservative and includes Achillesstretching and the use of viscoelastic heel cups in all shoes.Spontaneous resolution is the usual course. A MRI is necessary to

Fig. 14. Sever’s Disease. Sagital T2 FS image demonstrate edema in the fatty marrow ofthe calcaneal apophysis (arrow).

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rule out a calcaneal stress fracture when considering the differentialdiagnosis for Sever’s disease as these findings often resolve after a 3-4week period of immobilization and thus, immobilization may beindicated in patients not responding to conservative therapy forSever’s disease [60].

7. Conclusion

Due to the increasing intensity and training of pediatric athletes,the frequency and severity of overuse injuries have also becomemoreprevalent. As it is a relatively recent phenomenon, the potential forlong-term deleterious effects have not yet been fully investigated.However, the possibility for permanent damage exists. Specifically,active skeletally immature athletes can yield chronic axial loadsultimately leading to overuse injury afflicting the spine and lowerextremities. Therefore, it is essential for radiologists to have acomprehensive understanding of these entities and of their imagingpresentation. Proper use of different imaging modalities can helpdetermine diagnosis, mitigate long-term consequences and minimizeunnecessary radiation exposure. Overall, as radiologists, we canhelp our pediatric athletic patients endure their intense long-termtraining regimens without putting them at risk for the long-termconsequences of their overuse injuries through early detection andclinical recommendations.

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