The symptoms of joint interlock mostly occur in the knee joint, which means that the knee joint cannot be stretched and flexed suddenly during the process of activity, and is in a semi-extension and semi-flexion state. It is characterized by a significant restriction or impairment of knee movement, accompanied by significant local pain and even localized pressure pain. After a small amount of localized joint movement, a pronounced joint popping occurs and the joint movement returns to normal, i.e., the joint is unlocked and can be flexed and stretched normally. Interlocking of the joint is usually caused by meniscal damage or the presence of free bodies in the knee joint, and occurs during weight-bearing activities in the knee joint such as climbing and walking up and down stairs. If interlocked joints occur frequently, a diagnosis should be made by MRI and surgery should be performed to repair or clean the joint.