Frequent and sudden misalignment of the knee may be related to rupture of the cruciate ligament, habitual sprains, congenital malformations of the joint development, and so on. 1. Rupture of cruciate ligament: Rupture of cruciate ligament of the knee without repair can cause joint instability, which leads to joint misalignment when walking and symptoms such as limp legs. 2. Habitual sprains: due to the lack of timely rest and immobilization after trauma, the strength of the ligaments can not be restored, thus causing joint laxity, resulting in knee sprains and misalignment during activities. 3. Congenital malformation of joint development: mostly due to the congenital abnormal development of the knee joint, the patella sliding track on the femur is abnormal, the patella dislocation occurs after the knee joint is flexed and reset after straightening, the knee is often suddenly dislocated and then recovered immediately. There are other reasons that can cause the knee part often suddenly dislocated and immediately recovered, it is recommended to consult a doctor in a timely manner, improve the relevant examination, after clarifying the cause of the disease, follow the doctor’s instructions to further choose a reasonable treatment program to avoid delaying the condition.