Patients may report clicking, locking, and pain and swelling that is intermittent. While precedent trauma may exacerbate pain, it is not definitely causative and many patients do not recall any specific trauma; OCD seems to be a kind of repetitive-use injury, but its exact etiology is unknown. The average adolescent has had symptoms for 14 months at the time of presentation. Some patients report the knee will occasionally 'give out' on them during exercise.
Physical exam is often subtle or unremarkable. Patients may have a small amount of swelling or tenderness over the medial femoral condyle or no findings at all. Examination of the knee with higher-stage or larger lesions may reveal quadriceps weakening and limited full extension. Medial condyle lesions may have a positive Wilson's test in which the knee is internally rotated and extended from 90 degrees. A positive test is increased pain at 30 degrees or if pain is relieved by external rotation. Wilson's sign (walking with the knee externally rotated to avoid impingment of the fragment on the condyle) may also be present.