Le genou dégénératif: Du ménisque à l'os sous-chondral

The articular disorders vary with patient's age. This article presents some typical imaging features of degenerative lesions of meniscus, cartilage, and subchondral bone of the knee. Typical degenerative meniscal tears are horizontal, sometimes with displaced flaps. Radial tears of the posterior horn of the medial meniscus are less frequent but easily overlooked lesions. Cartilage loss is evaluated by the measurement of joint-space. However, this measurement is only valid when the two articular cartilage surfaces are in direct contact with each other (weight-bearing). Sometimes, the peculiar eburnated appearance of the subchondral bone makes it possible to recognize severe lesions ignored by nonvalid radiographs. Finally, a disorder of the subchondral bone marrow typically occurs in elderly: spontaneous osteonecrosis of the medial femoral condyle, which is probably the result of subchondral insufficiency fractures. Its early diagnosis is difficult, even with MRI, and requires very careful search for subchondral bone marrow abnormalities.