Osteoarthritis of the knee, is the most common joint disease of middle-aged and elderly people. Osteoarthritis is a disease caused by degeneration and wear of joint cartilage. Its basic pathological changes are degeneration of joint cartilage, subchondral bone sclerosis and bone redundancy formation, which can cause symptoms such as joint pain, swelling, restricted movement, difficulty in walking with weight, and advanced joint deformation. The course of the disease is recurrent and chronic, with a high rate of knee joint failure. In early osteoarthritis, the main treatment is conservative, and the patient should receive regular medication, quadriceps functional training and physical therapy, braces, orthotics and walking aids as ordered by the doctor. In advanced osteoarthritis, significant deformity has developed, the joint space is significantly narrowed or disappeared, and the symptoms continue unabated, then joint replacement surgery should be performed. However, the most common form of osteoarthritis is mid-stage osteoarthritis, with occasional swelling of the joint, frequent pain, and symptoms of strangulation or seizure, which affects the quality of life to some extent, then arthroscopic treatment with arthroplasty + cleanup is the best option. Osteoarthritis is not only a disease of the articular cartilage, it is a disease that involves the bone, synovium and the supporting structures around the joint. The destruction of cartilage and bone results in an increased amount of debris in the joint that is removed by phagocytes in the synovium, leading to synovial hyperplasia and hypertrophy. Articular cartilage degeneration, as well as synovial hyperplasia and chronic inflammation, are the main causes of joint pain and dysfunction. A large number of clinical practices illustrate that synovectomy has the effect of reducing swelling, relieving pain and improving joint function. With the development of arthroscopic technology, arthroscopic shaping+clearing of osteoarthritis has achieved better results than open surgery and has the advantages of less trauma, faster postoperative recovery, fewer and milder complications, and repeatability when necessary. It is possible to simultaneously remove free bodies, trim the bony flab of joint surfaces and joint edges, trim and shape the cartilage of worn joint surfaces, trim the meniscus, and release adhesions, etc. It is possible to restore the flatness of the surfaces of the movable structures in the joints, remove the pathological joint cartilage, stimulate the differentiation of osteogenic cells with differentiation ability to cartilage, and regenerate and repair the cartilage surfaces. The large amount of intraoperative joint cavity irrigation fluid with certain pressure not only removes cartilage, necrotic tissue debris and inflammatory mediators (such as prostaglandins, interleukins, tumor necrosis factor, etc.), but also adjusts the osmotic pressure, acidity and alkalinity of joint fluid and replenishes electrolytes, which improves the internal environment of the joint and allows the synovial inflammation to subside rapidly and normal synovial fluid to be restored. Although arthroscopic arthroplasty + cleanup cannot completely remove the cause of osteoarthritis and restore its normal anatomical structure, it can remove and repair the disease-causing tissue and inflammatory mediators in the joint, restore the flatness of the joint surface, and improve the intra-articular environment, thus interrupting the vicious cycle of osteoarthritis and having a positive effect on the treatment of osteoarthritis. Simply put, a normal knee joint is like a newly renovated house that is flat and shiny, but as time passes, the walls peel and the floor becomes dusty, and osteoarthritis occurs just like this. An arthroscopic cleanup is a major cleaning of the joint to remove the old material from the joint without affecting the joint structure, and this cleaning can be done several times. Arthroscopic surgery is minimally invasive and the risks are minimal compared to other procedures and are basically limited to the risk of anesthesia. The chances of postoperative infection are very low. Thrombophlebitis is also a potential risk for arthroscopic surgery. The incidence of deep vein thrombosis is low and is related to the use of tourniquets and the age of the patient. Other possible complications include instrument fracture, joint hematoma, and nerve injury, but are more rare than DVT. Recovery from arthroscopy is relatively rapid, usually returning to preoperative status 2 to 4 weeks after surgery, but further functional recovery may last longer. Furthermore, other procedures such as osteotomy or arthroplasty can be performed later, and arthroscopic arthroplasty+cleaning or grinding techniques do not increase the difficulty of these procedures. Arthroscopic arthroplasty + debridement should be used in patients who are active, older, have mild to moderate symptoms, and have failed conservative treatment. Case selection should be based on: medical history, physical examination and radiographic presentation. Age should not be the only criterion for selecting arthroscopic debridement. Patients with shorter duration of symptoms and predominantly mechanical symptoms have better postoperative results. patients with poorly aligned x-rays, especially those with exostosis, have poorer postoperative results. The following are a few indications for arthroscopic treatment: 1. joint pain, swelling, gradual onset of motion limitation, recurrent joint effusion, and no excessive joint space narrowing on imaging; 2. patients with clinical symptoms and imaging changes, but the degree of pain is disproportionate to the imaging performance, or patients treated by conventional medical methods but fractures occur 3. patients with chronic, stable (imaging) osteoarthritis that 4. Patients with osteoarthritis with primary mechanical motion disorders. The “ideal” patient is one who has a near normal femur-tibia alignment and whose function is indeed affected by the formation of bone fragments. Patients with degenerative meniscal tears resulting in mechanical symptoms usually have better outcomes than those with degenerative meniscal tears plus full thickening of the articular cartilage.