Chondromatose du genou compliquée d'un genou valgum secondaire avec compression de nerf sciatique poplité externe

Chondromatosis is a rare chronic arthropathy characterized by a synovial metaplasy inducing osteocartilaginous bodies formation into the joint cavity. We present a rare case of a giant chondrome compressing the common peroneal nerve and complicated by genu valgum with cartilage degradation in the outer compartment. We report an observation of a 25 year old man presenting for a knee swelling occurred 2 years before. Examination objectified three mobile masses at the level of his knee, stiffness estimated at 10 ° of extension and at 110° of flexion and especially nocturnal paresthesias at the level of the dorsal surface of his foot without motor deficit and manifestation of genu valgum involving the right leg estimated at 12 °. Radiographs of the knee (A and B) and MRI (C) objectified three radiopaque bone formations with large posterior osteophytes of the lateral femoral condyle. Surgical exploration revealed a partial compression of the common peroneal nerve (D) by one of these formations which lodged on the outer side of his knee. Then we made ablation of all visible cartilaginous masses (E).