The so-called ligament ossification is mainly caused by edema and spasm of the ligament after injury or after repeated strain on the ligament area for a long time. Later on, it leads to stiffness of the ligament and, in severe cases, to a gradual increase in the hardness of the ligament, resulting in ligament ossification (a marked increase in the hardness and density of the ligament, which is the same as that of the bone). This condition seriously affects the ligament laxity and causes significant pain in the ossified ligament area. The pain is especially aggravated during flexion, extension, and weight-bearing activities of the joint, which seriously affects the weight-bearing and flexion and extension activities of the limb.