Locked Superior Patellar Dislocation.

Superior dislocation of the patella is a rare cause of knee locking, with fewer than 20 cases reported in the English literature. The vast majority of traumatic or even atraumatic knee locking cases are due to such varied conditions as meniscal tears, osteochondral lesions, osteoarthritis, and ligamentous tears. A careful examination with proper radiographic imaging must be undertaken to properly evaluate patients who present with a locked knee, as they may have interdigitating patellofemoral osteophytes. An unusual case of a locked knee secondary to interlocking osteophytes between the femoral condyle and the inferior pole of the patella without a history of trauma is presented. The authors show how local sedation and gentle reduction are usually sufficient treatment, and that the vast majority of patients with this injury quickly return to their baseline functional level without the need for general sedation or surgical treatment.