Magnetic Resonance Imaging Patterns of Common Injuries in Pediatric and Adolescent Athletes

Abstract

Injuries in pediatric and adolescent athletes continue to rise in the United States, with increases in year-round sports participation, earlier sport specialization, and inadequate access to neuromuscular training programs. In this setting, the use of magnetic resonance imaging (MRI) provides a critical diagnostic tool. This review article describes the utility of MRI in diagnosing common pediatric and adolescent sports injuries and presents imaging findings associated with these pathologies.

Introduction

Participation in youth sports is increasingly popular among the pediatric and adolescent population in the United States, with an estimated 60 million children participating in recreational sports and over 8 million adolescents participating in high school sports [20,21,39,60]. In addition, there has been a recent trend toward more frequent and earlier sports specialization, associated with an increased risk for acute and chronic overuse injuries in young athletes [20,39,46]. Studies have demonstrated sports-related injuries may account for up to 53% of musculoskeletal complaints in pediatric and adolescent patients [57]. As a result, sports medicine physicians must understand the common injury patterns of this patient population. Magnetic resonance imaging (MRI) is an important tool in diagnosis, management, and surveillance of these injuries. This review aims to describe MRI findings of common upper and lower extremity injuries encountered in the pediatric and adolescent athlete, with associated case images. While standard radiographs are a mainstay of initial injury evaluation, given the preponderance of soft tissue injuries in this population, the evaluation of plain radiographs is beyond the scope of this review.

MRI Protocol

Magnetic resonance imaging is superior to other imaging modalities, with increased spatial resolution and the absence of ionizing radiation, which should be avoided, when possible, in the pediatric population. The authors recommend field strength MRI of 1.5 or 3.0 Tesla with the use of an extremity coil for upper and lower extremity joints for evaluation of sports medicine injuries in young patients. In addition, all pediatric joint MRI should include the addition of a fat-suppressed gradient-recalled echo (SPGR) sequence to evaluate the physis [22]. At our institution, SPGR sequences are routinely performed in the sagittal plane for ankle and knee and in the coronal plate for shoulder, elbow, hip, and foot.

Shoulder

Proximal Humeral Epiphysiolysis

Proximal humeral epiphysiolysis, also known as “little league shoulder,” is a common cause of shoulder pain in pediatric and adolescent overhead athletes [9]. Often presenting as pain with throwing activities, the injury results from repetitive torsional and tractional stresses on the shoulder, resulting in cumulative injury to the proximal humeral growth plate.

Initial imaging evaluation often begins with standard radiographs, which may demonstrate widening and irregularity of the proximal humeral physis (Salter-Harris I injury). However, these findings may be subtle, and standard radiographs are limited in their evaluation of other soft tissue pathology. In little league shoulder, MRI typically demonstrates bone marrow edema on both the metaphyseal and epiphyseal sides of the proximal humeral growth plate, physeal widening, and adjacent periosteal edema (Fig. 1) [32]. Less common findings include demineralization, sclerosis, fragmentation of the physis, and cystic changes [32]. Importantly, up to 30% of asymptomatic little league baseball players may demonstrate edema or widening of the proximal humeral physis on MRI, such that clinical history and examination remains paramount [59].

Fig. 1.

Coronal inversion recovery MRI demonstrating high signal fluid tracking into the widened proximal humeral physis (yellow arrow). MRI magnetic resonance imaging.

Coracoid Fracture

Scapular fractures account for < 1% of all pediatric and adolescent fractures, with the majority involving the coracoid [58]. Notably, displaced coracoid fractures are often associated with acromioclavicular (AC) joint dislocations in high energy injury mechanisms. However, repetitive overhead activities may result in injury of the coracoid physis, due to traction of the tendinous attachments of biceps, coracobrachialis, and pectoralis minor [58]. The coracoid has 3 ossification centers: at its base, at its apex, and at the attachment of the coracoclavicular ligament [53]. The physis at the base of the coracoid closes at approximately 14 to 16 years of age, predisposing young overhead athletes to apophysitis and apophyseal fractures in this location [58].

Coracoid fractures may be missed on plain radiographs, due to difficulty distinguishing Salter-Harris I injuries from a normal apophyseal plate. Magnetic resonance imaging allows for evaluation of the apophysis and surrounding soft tissue attachments. Growth plate injury to the coracoid is associated with widening, irregularity, and increased T2 hyperintensity on MRI (Fig. 2a, b) [1]. Alaia et al found that 0 of 8 patients with a coracoid injury were suspected to have a physeal injury prior to MRI, highlighting the importance of MRI for accurate diagnosis [1].

Fig. 2.

(a) Axial inversion recovery MRI demonstrating high signal intensity and separation at the coracoid physis. (b) Oblique sagittal inversion recovery MRI demonstrating edema and high signal fluid inferior to the coracoid, tracking into the base of the coracoid physis. MRI magnetic resonance imaging.

Bankart Lesion

Traumatic instability of the glenohumeral joint is a common injury in youth athletes, and increased frequency is associated with high-level sports participation [71]. Adolescent males participating in contact sports are at the highest risk for both first-time and recurrent anterior glenohumeral joint dislocation [62]. Although standard radiographs are useful for initial diagnosis and confirmation of adequate joint reduction, MRI is essential to evaluate associated soft tissue injuries, which may predispose these patients to recurrent dislocation events if not treated appropriately. Glenohumeral instability may result in secondary bony and soft tissue injury to the shoulder complex, including labral tears (bony and soft tissue Bankart lesions), humeral avulsion of the glenohumeral ligament lesions, glenoid labral articular cartilage defects, and anterior labral periosteal sleeve avulsions (ALPSAs) (Fig. 3) [47,73]. In a group of patients with either acute or chronic dislocations, Bankart and Hill-Sachs lesions were identified in approximately 90% of patients, whereas ALPSA lesions were in only 10% of patients [73].

Fig. 3.

Axial inversion recovery MRI demonstrating anterior labral tear with a small fracture of the anterior glenoid (yellow arrow), consistent with a bony Bankart lesion. MRI magnetic resonance imaging.

Importantly, Sidharthan et al demonstrated that glenoid ossification patterns may mimic Bankart lesions on MRI of the shoulder [67]. However, much like for coracoid fractures, the predictable pattern of glenoid ossification can help with distinguishing normal growth from injury, as the anterior secondary ossification center is the last to fuse (females: age 11–12; males: age 11–17) and should not be confused with a Bankart lesion [67].

Elbow

Medial Epicondyle Apophysitis

A significant number of young athletes participate in overhead throwing sports, with more than 2 million children and adolescents participating in youth baseball alone [74]. The overhead throwing motion places significant valgus load across the elbow joint, thereby placing stress on the static and dynamic stabilizers of the medial elbow, including the ulnar collateral ligament (UCL), flexor-pronator musculature, and the medial epicondyle [8,18,48]. With earlier sport specialization, increased pitch counts, and increased pitch velocities, the incidence of medial elbow injuries in young athletes continues to increase.

In patients aged 14 to 16 years old, the medial epicondyle apophysis may remain open. Medial epicondyle apophysitis, commonly referred to as “little league elbow,” results from chronic valgus loading of the elbow during the throwing motion. This repetitive stress results in MRI demonstrating progressive widening and inflammation of the medial epicondylar apophysis, with associated medial elbow pain (Fig. 4) [72].

Fig. 4.

(a) Coronal spoiled gradient-recalled echo (SPGR) MRI demonstrating widening of the medial epicondylar physis (yellow arrow). Of note, the radial head, capitellar, and medial epicondylar physes remain open. (b) Coronal inversion recovery MRI demonstrating high signal fluid in the medial epicondylar physis. MRI magnetic resonance imaging.

Medial Epicondyle Apophyseal Avulsion Fracture

Occasionally, repetitive or acute excessive valgus load may lead to medial epicondyle avulsion fracture [18,27]. Medial epicondyle fractures account for 12% to 20% of elbow fractures in pediatric and adolescent patients, often associated with a fall onto an outstretched arm [18,27]. However, a small proportion of these fractures may be associated with overhead activities and result in complete separation of the medial epicondyle apophysis, typically with anterior and distal displacement of the fragment [18].

UCL Tear

After bony fusion of the medial epicondyle apophysis, the failure mechanism for the medial elbow under valgus stress becomes predominantly soft tissue in nature. The anterior oblique bundle of the UCL is the primary restraint to valgus stress during the throwing motion, and thereby the most predisposed to injury [18]. Joyner et al described an MRI-based classification for UCL injuries: type I: edema only in UCL fibers; type II: partial tear UCL without extravasation of joint fluid; type III: complete tear with extravasation of joint fluid (Fig. 5); and type IV: tear/pathology in more than 1 location (ie, proximal and distal), with increased injury severity correlated with the amount of clinical valgus laxity [40]. Prior studies have shown that adolescent athletes more commonly demonstrate partial thickness tears compared with adult athletes [26]. Nevertheless, the incidence of UCL reconstruction in the United States has continued to rise. Mahure et al recently reported a 343% overall increase in the incidence of UCL reconstruction, with 57% of these procedures performed in patients 15 to 19 years of age [48]. The authors also projected a disproportionate increase in rates of UCL reconstruction in this young population through 2025 when compared with older athletes [48,74].

Fig. 5.

(a) Coronal inversion recovery MRI demonstrating mid-substance tear (yellow arrow) and (b) distal tear (yellow arrow) of the ulnar collateral ligament. MRI magnetic resonance imaging.

Osteochondritis Dissecans of the Capitellum

In contrast to valgus stress, repetitive and forceful axial loading of the elbow joint may predispose young athletes to the development of osteochondritis dissecans (OCD) lesions of the capitellum, similar to OCD lesions in other locations (eg, knee and talus). The etiology of these lesions is unknown, but likely results from a combination of vascular ischemia, microtrauma, and genetic factors [16,45]. Surgical versus non-surgical intervention is often predicated on the stability of the lesion. Several prior studies have demonstrated MRI-based criteria as the best predictor of intra-operative OCD lesion stability, including high signal rim and high signal interface on MRI (Fig. 6) [8,38,64]. Recent studies have also demonstrated return to sport rates > 80% following surgical management of capitellar OCD lesions, including 89% in overhead athletes.

Fig. 6.

Sagittal proton density MRI demonstrating capitellar OCD lesion with an unstable in-situ fragment, with discontinuity of the overlying cartilage (yellow arrow). MRI magnetic resonance imaging, OCD osteochondritis dissecans.

Hip/Pelvis

Labral Tear

Specific sports, including soccer, football, and ice hockey, have been associated with higher rates of hip injuries in young athletes [65]. Common injuries in this patient population are predominantly soft tissue pathologies, including labral tears, apophysitis, and apophyseal avulsion fractures [68]. Traumatic bony injuries involving the hip are uncommon in pediatric and adolescent patients and are beyond the scope of this review.

In young, active patients, labral tears are most commonly associated with femoroacetabular impingement (FAI; either cam or pincer lesions), and may be associated with groin pain with activities or mechanical symptoms [24]. Cam lesions lead to shear force being asymmetrically distributed across the anterosuperior acetabular cartilage and labrum, whereas pincer morphology leads to the overgrown acetabular rim directly contacting the anterosuperior labrum, leading to degeneration and eventual tearing [66]. In contrast to plain radiographs or computed tomography imaging, MRI allows for visualization of both bony (ie, pincer and/or cam lesions) and soft tissue abnormalities (ie, labral tears, cartilage defects, synovitis) [52,57]. Prior MRI studies have demonstrated that labral tears are most commonly identified at the anterior aspect of the labrum, as evidenced by high signal intensity fluid at the chondrolabral junction (Fig. 7) [52].

Fig. 7.

Sagittal proton density MRI demonstrating anterior labral tear with associated ganglion cyst formation (yellow arrow). MRI magnetic resonance imaging.

Apophysitis of the Hip/Pelvis

In contrast to elbow apophyses discussed previously, the pelvic apophyses typically fuse at older ages (~20 years old), thereby predisposing older adolescents to injury at these location [6]. The most commonly injured are the anterior superior iliac spine (ASIS), the anterior inferior iliac spine (AIIS), and the lesser trochanter, as the musculotendinous attachments at these locations are involved in running and kicking motions [23]. Repetitive traction forces can ultimately lead to inflammation at the apophysis leading to apophysitis. Patients being evaluated for apophysitis often present with negative radiographs; however, MRI may demonstrate mild apophyseal widening, high signal edema, and inflammation (Fig. 8a) [2,57].

Fig. 8.

(a) Coronal inversion recovery MRI of the pelvis demonstrating soft tissue edema at the right anterior inferior iliac spine (yellow arrow) and (b) Sagittal proton density MRI demonstrating avulsion fracture of the anterior inferior iliac spine at the rectus femoris origin (yellow arrow). MRI magnetic resonance imaging.

Apophyseal Avulsion Fracture of the Hip/Pelvis

As discussed above for the medial epicondyle, continued repetitive stress or an acute excessive load may lead to pelvic apophyseal avulsion fracture. Magnetic resonance imaging affords assessment of the associated soft tissue injury, including tendon integrity, displacement, and periosteal stripping in the acute setting (Fig. 8b) [36,57]. If clinical presentation is delayed and there is significant callous formation or osseous proliferation following fracture, distinguishing an avulsion fracture from chronic apophysitis may be difficult, even with MRI [6].

Knee

Patellar Dislocation

Patellar dislocation is a common injury among pediatric and adolescent patients, particularly those with valgus lower extremity alignment, patella alta, and trochlear dysplasia [3]. Following a patellar dislocation, MRI may be useful for confirmation of a patellar instability event, typically demonstrating injury to the medial patellofemoral ligament (MPFL) and significant bony edema of the lateral trochlea/medial patellar facet (Fig. 9). In addition, MRI allows for identification of osteochondral injury or loose bodies, a common indication for operative intervention in the acute setting [28]. In contrast, plain radiographs demonstrate poor sensitivity for diagnosing loose bodies (~23%) and for osteochondral lesions (8%) [5]. Magnetic resonance imaging also allows for assessment of rotational and sagittal malalignment, which is essential for appropriate surgical decision-making. Numerous studies demonstrate the validity of MRI for the measurement of axial and sagittal tibial tubercle to trochlear groove distance and Caton-Deschamps index [4].

Fig. 9.

(a) Sagittal inversion recovery MRI demonstrating cartilage shear injury (yellow arrow) of the lateral femoral condyle with a large knee effusion following acute patellar dislocation and (b) Sagittal proton density MRI demonstrating loose body anterior to the medial meniscus (yellow arrow). MRI magnetic resonance imaging.

Discoid Meniscus

Discoid meniscus most commonly affects the lateral meniscus and results from disorganized, immature meniscal tissue that is predisposed to degeneration and tearing as a result of altered biomechanics [41]. Magnetic resonance imaging criteria for diagnosis of a discoid meniscus includes: (1) continuous meniscal tissue between the anterior and posterior horns on 3 consecutive 5 mm thick sagittal slices, (2) > 15 mm meniscal body width on a coronal sequence, or (3) minimum meniscus width > 20% of the maximal total tibial plateau width [63]. While MRI demonstrates higher sensitivity for the detection of intrasubstance tearing when compared with traditional gold-standard arthroscopy [31], caution must be used and clinical history/exam taken into consideration due to the high prevalence of asymptomatic peripheral meniscus signal irregularities seen in children [69].

Juvenile OCD of the Knee

Juvenile OCD is a disorder of the subchondral bone of unknown etiology; it leads to delamination of the overlying articular cartilage, possibly from repetitive trauma and resulting vascular insult [70]. In about 2/3 of cases, juvenile OCD of the knee affects the lateral aspect of the medial femoral condyle [56]. Magnetic resonance imaging is most typically used for characterization of OCD lesions, particularly for evaluating lesion instability. De Smet et al defined lesion instability as: (1) a high signal line on T2 MRI at the bone-fragment interface suggestive of joint fluid or fibrovascular granulation tissue, (2) cyst formation beneath the lesion, (3) focal cartilage and subchondral region defects with fluid in the base, and (4) focal articular surface defect (Fig. 10) [19]. The Hefti and Kocher classifications are established classification schema for OCD based on MRI characteristics; they focus primarily on differentiating stable and unstable lesions to guide treatment strategies [35]. However, the sensitivity and specificity of these schema and others demonstrate wide variability [14,34]. Ultimately, arthroscopic description of OCD lesions is performed using the Research in Osteochondritis of the Knee (ROCK) classification, which broadly distinguishes these into immobile and mobile lesions [56].

Fig. 10.

(a) Coronal proton density MRI demonstrating stable medial femoral condyle OCD lesion and (b) Inversion recovery MRI demonstrating unstable medial femoral condyle lesion with high signal fluid undermining the progeny lesion. MRI magnetic resonance imaging, OCD osteochondritis dissecans.

Tibial Spine Fracture

Tibial spine fractures are a uniquely pediatric pathology, which occur in skeletally immature patients as a result of higher strength of the anterior cruciate ligament (ACL) compared with the ossifying tibial spine [17]. Traditionally, classification of tibial spine fractures was performed on standard radiographs [51]. More recently, Green et al described a similar MRI-based classification based on fragment displacement, extension, and involvement of either meniscus, with grades (1) non-displaced or minimally displaced fractures (≤ 2 mm); (2) fractures with intact posterior hinge and > 2 mm of anterior displacement but ≤ 2 mm posterior displacement; and (3) > 2 mm of posterior displacement, an entrapped meniscus, or extension beyond the spine into the plateau (Fig. 11) [29]. Particularly among younger patients, the fracture bed of tibial spine fractures may further extend to the posterior third of the tibial epiphysis into the weight-bearing surface in up to 50% of cases [15]. Magnetic resonance imaging is particularly useful for the detection of (1) concomitant meniscal entrapment/tears (most commonly the anterior horn of the medial meniscus), which may block reduction attempts and (2) concomitant ACL injuries that may require surgical management and is a known risk factor for post-operative arthrofibrosis [12].

Fig. 11.

Sagittal inversion recovery MRI demonstrating type II tibial spine avulsion fracture with intact ACL fibers (yellow arrow). ACL anterolateral complex, MRI magnetic resonance imaging.

Ankle

Lateral Ankle Sprain

In pediatric and adolescent athletes, ankle and foot injuries account for between 22% and 36% of all injuries [49,61]. Although ankle fractures are common [33,54], soft tissue injuries (including lateral ankle sprains) may account for 12% of all musculoskeletal injuries in young athletes [61]. The majority of lateral ankle sprains result from an inversion injury and are often successfully treated non-operatively with bracing and physical therapy. However, prior studies have demonstrated persistent, chronic ankle instability in up to 1/3 of adolescents following these injuries [30]. Plain radiographs are the mainstay of screening for associated fractures, but MRI may be useful in the setting of chronic pain, instability, or mechanical symptoms following lateral ankle sprains. Typically, MRI of lateral ankle injuries in adolescents demonstrates injury to the lateral ligament complex (including the anterior talofibular ligament and calcaneofibular ligament) [43].

Syndesmotic Injury

Injuries to the syndesmosis, also known as “high ankle sprains,” may occur in young athletes. The ankle syndesmosis is comprised of the posterior inferior tibiofibular ligament, the anterior inferior tibiofibular ligament, and the interosseous membrane. Injury mechanisms involving forceful external rotation of the ankle may cause disruption of one or more components of the syndesmotic complex with or without involvement of the deltoid ligament, resulting in ankle instability. Prior studies have demonstrated that 22% of ankle injuries in high school athletes involved syndesmotic injury and 7% involved the deltoid ligament [43]. Magnetic resonance imaging may be used to evaluate ligamentous injury, associated bony edema, or avulsion fractures (Fig. 12) [6,25].

Fig. 12.

(a) Axial proton density MRI demonstrating interosseous ligament tear (yellow arrow) and (b) Avulsion of the anterior tibiofibular ligament (red arrow). MRI magnetic resonance imaging.

OCD of the Ankle

The ankle is the second most common location for OCD formation (following the knee) in the pediatric and adolescent population [13,44]. Ankle OCD lesions most commonly occur in the posteromedial (72%) and anterolateral talus (22%) [13,44]. Similar to the other OCD lesions described above, MRI is an essential tool in the evaluation of lesion location, size, and stability as it allows for assessment of associated bony edema, fluid signal hyperintensity, and cartilage defects with or without loose body formation [13,44].

Metatarsal Stress Fracture

In young athletes, the metatarsals are a common site of chronic overuse injuries, due to the high axial loads associated with running and jumping, particularly during the push-off phase of gait. Prior studies have demonstrated the metatarsals as the second most common location for stress fractures (following the tibia) in this patient population; these fractures are associated with endurance activities, and most commonly involve the second and third metatarsals [10,37,42,55]. Stress fractures of the meta-diaphyseal junction of the fifth metatarsal are important to recognize, as they are associated with a high risk of non-union [7,10,37]. Magnetic resonance imaging is the preferred imaging modality for assessment of metatarsal stress fractures, allowing for assessment of associated bony edema, periosteal thickening, subtle fracture lines, and bony remodeling despite negative radiographs [6,10,11,37,50].

Conclusion

Continued increases in sports participation among pediatric and adolescent athletes, coupled with earlier sports specialization, result in a greater number of athlete exposures each year. Consequently, the number of acute and chronic sports-related injuries among young athletes continues to increase in the United States. Magnetic resonance imaging is a useful diagnostic, prognostic, and surveillance tool in the evaluation of these injuries, allowing for assessment of both bony and soft tissue pathology, without risk of radiation exposure in this vulnerable population.