The two x-rays show an osteoarthritis on the medial compartment of the knee: this unfortunate case is of a young 30 years old sportsman who had presented an anterior cruciate ligament tear when he was 15 years old. The anterior cruciate ligament tear had not been treated surgically. Evolution of the injury 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.