Osteochondritis dissecans of the trochlea of the femur.

This article defines the characteristic features of osteochondritis dissecans of the trochlea of the femur, and indicates that important differences distinguish it from the more familiar femoral condylar form. The clinical features in 16 knees included: gradual onset of symptoms, pain with running and jumping, no significant history of injury; inconstant tenderness of the trochlea, and pain with resisted extension at 20 to 45 degrees. Diagnosis was usually difficult, and was often delayed because of subtle radiographic changes. Treatment depended on the stage of presentation. Nonsurgical treatment failed in four of seven knees. Drilling the lesions failed in two of the three cases. Fixation with small screws produced two good results; two others healed, but with short follow-up. Removal of the loose bodies from six knees produced one poor result and five good results. This process differs in presentation from femoral condylar osteochondritis dissecans. Although the results (average follow-up more than 5 years) were generally good, the mild symptoms probably represent incongruity of the patellofemoral joint, and probably foretell osteoarthritis.