Osteochondritis dissecans of the knee.

Osteochondritis dissecans is a disorder in which a fragment of cartilage and subchondral bone separates from an articular surface. The etiology is uncertain, although trauma and ischemia have been implicated. The knee is most commonly affected, but the elbow and ankle may also be involved. Patients typically present during their adolescent or early adult years with nonspecific knee pain and swelling that worsens with activity. The diagnosis is confirmed by radiographic findings. Management decisions are based on the patient's age and the stability, location, and size of the lesion.