Sudden weakness of the ankle sometimes is common for the following reasons: First, talar exfoliative osteochondritis, caused by long-term repeated ankle joint overload, can lead to limited softening and fibrosis of the talar articular surface osteochondral bone, which in turn causes cartilage defects, bone exposure, fragmentation, edema, congestion and hypertrophy of the synovial membrane and fat pad, commonly found in soccer fans, the clinical manifestation is that the patient feels that when standing, walking, running and jumping The clinical manifestation is that the patient feels pain and swelling in the ankle joint with interlocking sensation when standing, walking or running and jumping. Examination reveals swelling of the ankle joint, painful squeezing of the joint space, limited movement of the ankle joint, audible friction sounds and friction sensation to touch, effusion of the ankle joint, X-ray may show narrowing of the ankle joint space and joint degeneration. Second, ankle joint free body, cartilage loss can form joint free body, free body into the ankle joint gap, can affect the ankle joint activities, resulting in sudden ankle joint weakness symptoms.