1. Osteoarthritis: It is the most common type of arthritis in clinical practice, with a high incidence in the middle-aged and elderly population, and can cause significant pain, dysfunction and difficulty in walking, seriously affecting patients’ quality of life. Osteoarthritis medications are usually limited to symptom control, with low efficacy, and are unable to alter and control the progression of the osteoarthritis disease. When conservative treatments such as medications fail to relieve and control symptoms, doctors often recommend that patients use arthroscopic flushing and cleaning to treat osteoarthritis of the knee. Arthroscopy is one of the most important means of treating osteoarthritis, and it is a method between conservative treatment and artificial joint replacement, which is very common nowadays. 2.Knee joint sports injury: such as meniscus injury, knee joint instability caused by posterior cruciate ligament injury. It can be cleaned up and reconstructed through arthroscopy. 3.Inflammatory arthritis: Inflammatory arthritis includes many types of joint lesions, such as rheumatoid arthritis and ankylosing spondylitis. Effectively controlling the development of synovitis is an important measure to reduce pain, delay the destruction of articular cartilage and maximize the maintenance of joint function. 1, the strict system of regular internal medicine conservative treatment for three to six months is ineffective, persistent joint swelling, oozing and pain is serious, X-ray examination of bone destruction is not obvious, should be carried out as soon as possible synovectomy. 2, although the course of the disease is less than half a year, accept drug treatment, but joint swelling and pain is obvious, clinically palpable hypertrophy of the synovial membrane, it is also appropriate to carry out synovectomy. 3, joint lesions for more than 1 year, joint swelling, pain, X-ray examination has obvious osteoporosis or mild joint space narrowing, but there is no obvious bone destruction and deformity, indicating that the articular surface hyaline cartilage or inter-articular fibrocartilage (meniscus, etc.) has been different degrees of destruction. At this time, although synovectomy has been unable to achieve the role of protection of articular cartilage, but to prevent further destruction of articular cartilage, reduce pain, delay the time of arthroplasty, can also play a certain role. 4, septic arthritis: most of the septic arthritis to a single joint onset, usually catastrophic disease. Early and thorough cleanup of infected lesions in the joints is the key to treating septic arthritis. Early diagnosis and early treatment reduce the risk of loss of joint function. When a diagnosis of septic arthritis is considered, aggressive surgical intervention is advocated. If diagnosis and treatment are delayed, serious consequences can occur, including osteomyelitis and joint destruction. With arthroscopic debridement, necrotic tissue, fibrin deposits of inflammatory synovial tissue, and pus moss are thoroughly cleaned out sequentially under direct arthroscopic visualization, large volumes of saline are flushed, and drainage tubes are effectively placed under direct arthroscopic visualization to allow for proper placement of drainage tubes, and postoperative antibiotic saline flushes are performed to continue to flush out the necrotic tissue and keep inflammation under control. Arthroscopic cleanup combined with postoperative continuous irrigation is an effective treatment, safe and simple, with fast postoperative recovery and little trauma, which can rapidly control the development of the disease and favor the recovery of joint function.