Osteochondritis Dissecans of the Capitellum

Osteochondritis dissecans of the capitellum is one of the most important causes of lateral elbow pain in the adolescent athlete. It is distinct from Panner disease, which affects a younger child and the entire capitulum and is self-limiting. The key clinical decision is whether the lesion is stable or unstable.

Who. An adolescent of 11-16 years (peak 12-14) with an open physis: a baseball pitcher, gymnast, racquet player or cricket bowler. Males predominate (baseball, gymnastics). Over 80% of lesions involve the dominant arm, and bilateral lesions are reported in gymnasts, due to symmetrical loading.

Why it matters. Treatment means months away from sport, and 30-50% of symptomatic lesions require surgical intervention. Return to sport averages 6-12 months, and not every athlete returns to their prior level.

The cost of delay. Delayed diagnosis of an unstable lesion risks loose body formation, progressive arthritis and career-ending elbow dysfunction. In chronic cases the long-term risk is radiocapitellar joint degeneration.

The capitellum. The capitellum is the lateral articular surface of the distal humerus, articulating with the radial head. It is almost entirely covered by articular cartilage, which limits vessel access.

Blood supply. Blood reaches it through limited end-arterioles that enter posteriorly, with no collateral circulation to the subchondral bone, and in the skeletally immature the supply is tenuous.

The growing elbow. The capitellar secondary ossification centre is still developing through the peak sporting years, and skeletally immature bone is less resistant to microtrauma.

Mechanism. The radiocapitellar joint bears significant compressive load during throwing. Repetitive compressive loading across it (valgus stress in throwing, axial loading in gymnastics) causes microtrauma to the subchondral bone and compromised blood flow, leading to ischaemic necrosis of a focal segment. If loading continues, the overlying articular cartilage may separate, creating an unstable fragment or loose body.

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Natural history. Early diagnosis and activity modification can arrest progression through these stages:

• Early: subchondral bone oedema and ischaemia, reversible with rest
• Progressive: fragmentation of the subchondral bone with intact cartilage (stable OCD)
• Advanced: cartilage breach and fragment separation (unstable OCD)
• End-stage: loose body formation, an articular surface defect and early radiocapitellar arthritis

Stable lesions can heal with rest; unstable lesions generally require surgery. The staging below reads the lesion on radiograph and MRI, and two named systems, Minami on the radiograph and the ICRS-OCD at arthroscopy, are also worth quoting.

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Will it heal with rest? This is the single most useful prognostic question, and Takahara defined the practical predictors. A lesion is likely stable and healable with rest when all three are present:

• an open capitellar physis
• good elbow motion, with a flexion contracture under about 20 degrees
• a localised radiolucency or flattening with intact overlying cartilage

It is unstable and unlikely to heal, favouring surgery, when there is a closed or closing physis, a flexion contracture of 20 degrees or more, or radiographic fragmentation, a clear separation line or a loose body.

The physis dominates. Of these predictors, physeal status is the dominant factor. The open physis still has the biological capacity to revascularise and heal, whereas a lesion in the older adolescent with a closed physis behaves like an adult osteochondral defect. Pair the MRI stability read with the physis and the range of motion before committing a patient to months of rest.

History. Lateral elbow pain of insidious onset, worse with activity, in an adolescent overhead athlete or gymnast, often present for weeks to months before they seek attention. Take the training history: year-round play, high pitch counts, no off-season.

Mechanical symptoms. Clicking, locking or catching suggests an unstable lesion, and painful clicking or locking suggests an unstable lesion with a loose body.

Examination. The radiocapitellar joint is tender, and mild lateral elbow swelling from an effusion may be present. Loss of extension is the most common finding, and there may be a flexion contracture. The neurovascular examination is typically normal; rule out radial nerve entrapment.

Provocative signs. Look for pain with active forearm rotation (supination and pronation) against resistance, and for a palpable or audible click with motion, which suggests a loose body.

Radiocapitellar compression test. With the elbow in extension, apply an axial load through the forearm while pronating and supinating. This compresses the radial head against the capitellum, reproducing the mechanical pain, and pain localised to the lateral elbow is a positive test that suggests radiocapitellar joint pathology (OCD or Panner).

Radiographs first. AP, lateral and oblique views of the elbow; a 45-degree flexion lateral view improves visualisation of the capitellum. Look for a radiolucent area in the capitellum, flattening, sclerosis, fragmentation and loose bodies.

Their limits. Early OCD may be subtle or normal on radiographs, with sclerosis and lucency developing over time, and plain radiographs alone may underestimate lesion severity.

MRI is indicated in all suspected capitellar OCD and is the gold standard for staging. The critical finding is whether there is fluid signal between the fragment and the underlying bone on T2 sequences:

• Subchondral T2 hyperintensity with intact overlying cartilage and no fluid behind the fragment: likely stable, and may heal with rest
• Fluid signal between the fragment and the underlying bone (a high-signal T2 rim around the fragment), disrupted cartilage, a displaced fragment or a loose body: unstable, requiring surgical evaluation, and surgery is generally indicated

The MRI may also show subchondral cyst formation or a clear fracture line.

CT is not routine: it is reserved for surgical planning rather than initial staging. It better delineates bony architecture, and assesses fragment size, location and bone quality before fixation or OATS.

Prevention. The most effective strategy for capitellar OCD is prevention. Adolescent baseball pitchers should adhere to age-appropriate pitch count limits, take at least 3-4 months off from overhead throwing per year, and avoid pitching for multiple teams simultaneously. Gymnasts should have scheduled rest periods and avoid year-round training without breaks. Any lateral elbow pain in a young athlete warrants evaluation before resuming sport.

Prognosis. The stability of the lesion on MRI is the most important prognostic factor, and stable lesions have a high rate of healing with rest alone. Beyond stability, the prognosis is best with younger age, early diagnosis, complete activity cessation and high compliance. It is poor in the older adolescent near physeal closure, and with a large defect, multiple loose bodies or poor compliance with rest.