The two x-rays show a knee osteoarthritis on the medial compartment : this unfortunate case is of a young 30 years old sportsman who had presented a rupture of the anterior cruciate ligament when he was 15 years old. The lesion had not been treated surgically. Evolution of the rupture of an untreated ACL is not always so fast, nor so severe. This illustration in any case shows the possible need for surgical reconstruction in a young motivated sportsman, who wishes to continue with his sport.