(a) Diagnostic role First, arthroscopy can be used to examine various lesions in the joint cavity and to evaluate and record in detail the condition of various tissues and structures in the joint. Certain joint lesions, such as pigmented villous nodular synovitis, have characteristic arthroscopic manifestations, and the diagnosis can almost be made. At the same time, joint fluid or diseased tissue can be obtained and biopsied under arthroscopic surveillance for further laboratory and pathologic examination. However, with the development of various non-invasive tests in recent years, especially ultrasound, CT and MRI imaging, arthroscopy for purely diagnostic purposes has been used less and less in clinical practice. However, arthroscopy can observe and explore the lesion under direct vision, and has a certain magnification effect, and can also be used for dynamic observation, which has irreplaceable advantages. Therefore, it is still valuable for patients who cannot clearly identify the cause of the disease for a long time after clinical physical examination and various auxiliary examinations. (ii) Therapeutic role In addition to the therapeutic role of a variety of sports injuries, arthroscopic techniques can also play an important role in the surgical treatment of arthritis. It has been reported in the literature that arthroscopic techniques can be used in the diagnosis and treatment of various types of arthritis, including osteoarthritis, inflammatory joints, pigmented villous nodular synovitis, crystalline arthropathy, infectious arthritis, and traumatic arthritis. For example, for many types of synovitis, synovectomy can be performed arthroscopically. In the knee, synovial tissue can be removed from the posterior joint capsule through a posterior approach to achieve total synovectomy of the joint capsule. In osteoarthritic joints, arthroscopic debridement is performed to remove free bodies, remove torn menisci, and trim cartilage surfaces.