It may be the result of joint degeneration. After arthroscopy, there is usually a joint swelling period of 1-3 months or even longer, and the joint snapping is caused by the degeneration and wear of patellofemoral joint surface. It is difficult for articular cartilage degeneration to return to normal. Oral glucosamine and intra-articular injection of sodium hyaluronate can be used. Symptoms can be alleviated.