Bilateral patellar osteochondral defects

A 15-year-old rugby player who sustained a right knee direct injury. Since the injury he had intermittent right knee swelling associated with any form of strenuous activity. Clinical examination revealed an effusion in the right knee. The left knee was far less symptomatic, with only occasional pain and crepitus.

Radiographs of the right knee (Fig. 1) demonstrated a large joint effusion and normal osseous structures. An MR study (Fig. 2 – right knee; Fig. 3 – left knee) revealed bilateral focal osteochondral defects in the medial patellar facets.

Osteochondral lesions / defects (OCD) are a common pathology of subchondral bone and overlying cartilage in children and adolescents. The most common joint to suffer from an OCD is the knee joint, involving the medial femoral condyle, with the patella being a rare location. The presence of bilateral and symmetrical patellar osteochondral defects is even rarer and in the English literature, only a few cases have been described [1, 2].
The aetiology of OCDs is not fully elucidated. According to common hypotheses, repetitive microtrauma, local ischaemia, disturbance of normal ossification of accessory centres during maturation and hereditary factors are considered contributory to pathophysiology of OCD.
It is a well-known fact that OCD predisposes a patient to an early degenerative change in the joint.
From imaging perspective radiography is the first modality is used to diagnose OCD and monitor healing process. However, MRI is the most accurate and sensitive tool which enables to diagnose OCD at early stages, grade OCD process and determine a lesions’ healing potential. A fluid-like signal at the interface of the OCD and the native bone is indicative of instability. However, at times it is difficult to confidently conclude whether an osteochondral defect is stable or not and in these cases arthroscopy has a major role not only in confirming the stability of an of OCD, but in treating the lesion.
Treatment of OCD varies widely depending on the age of patient and the stage of OCD from activity adjustment and reduced weight bearing (stable, less severe disease) to operative management (unstable defect). Surgical treatment is reserved for patients who do not improve with conservative treatment or with a suspected unstable lesion. Operative procedures include debridement, microfracture, osteochondral autografting and autologous chondrocyte implantation.
A better prognosis is associated with early age; for instance in juvenile group healing potential is up to 75% [3] whereas in the adolescent group is about 50% and in the adult group chances of healing are low even with advanced treatment. The important factors influencing prognosis include size and location of the lesion, duration of the symptoms, fragment stability and appearances of the overlying cartilage.

Take Home Messages:
• MRI is the most useful and sensitive technique in evaluating and staging OCD.
• Presence of fluid-like signal at the interface of OCD and native bone is indicative of instability.
• Bilateral patellar OCD is probably underestimated as often contralateral knee is asymptomatic.

Written informed patient consent for publication has been obtained.