There is synovial tissue in the suprapatellar capsule of the human knee joint, and the synovial membrane has a crease that extends into the cavity of the suprapatellar capsule. When the crease is caught between the patella and the femur and symptoms of pain, swelling, and restricted movement of the knee joint occur, synovial crease syndrome can occur. The main symptoms are: 1. pain: usually more obvious when extending the knee, because the knee joint often has a large contact area between the patella and the femur, when the synovial crease is caught between the patella and the femur, the pain of synovial crease syndrome will appear. 2. swelling: synovial crease syndrome is often accompanied by synovitis, there will be joint cavity and suprapatellar capsule fluid and swelling. 3. limitation of joint movement: when there is pain, the knee joint There is a significant restriction of movement. A diagnosis of synovial crepitus syndrome should be made by performing an MRI and physical examination to rule out other diseases. If severe pain is not relieved by conservative treatment, arthroscopic surgery should be considered.