The clinical application of arthroscopy provides a new means for the diagnosis and treatment of joint surgical diseases. With the understanding of joint anatomy, the improvement and perfection of arthroscopy, as well as the proficiency of operating techniques and the gradual expansion of application, arthroscopic surgery will gradually replace other methods of intra-articular surgery and form an independent diagnostic and treatment system and an independent discipline. Arthroscopy can be used for examination and diagnosis as well as a clinical tool for various surgeries. Indications: ① meniscal injury, cruciate ligament injury, unexplained articular cartilage injury of the knee joint; ② joint pain with obvious symptoms and no clear diagnosis for a long time; ③ synovitis and synovial lesions can be treated by biopsy or lavage of the suspected lesions at the same time as arthroscopy; ④ examination of intra-articular free bodies and foreign bodies and arthroscopic surgery, such as synovectomy for rheumatoid arthritis, etc. 2, contraindications: ① systemic or local infection, soft tissue damage or skin disease in the joint area; ② serious heart disease, uncontrolled diabetes or physical failure; ③ coagulation mechanism disorders; ④ joint ankylosis, severe scar contracture, joint cavity occlusion, joint capsule with large damage and other obstacles to joint expansion and affect the arthroscopic observation.