Because of the application of minimally invasive techniques in knee joint surface replacement, knee joint surface replacement surgery is no longer considered a major surgery, but even so, we have been very strict about the indications for knee joint surface replacement. According to the statistics on the results of arthroscopic surgery for all patients who underwent arthroscopic surgery to clean up their knee joints after previous non-surgical treatments failed, 85% of the patients who underwent arthroscopic surgery to clean up their knee joints were satisfied with the results of the surgery, but 15% of the patients had poor surgical results and had to undergo a second operation to replace their knee joints with artificial knee joint surfaces. A summary of the reasons for the ineffectiveness of these 15% of patients led to the following six common characteristics, which are our indications for knee replacement. In other words, if the condition of a patient with osteoarthritis or rheumatoid arthritis meets all of the following six criteria, we recommend that the patient undergo a knee replacement in order to prevent the patient from having to undergo a second surgery if the patient fails to respond to the surgery. These six conditions are: 1. Osteoarthritis of the knee joint pain, swelling and going up and down the stairs, the knee joint can not exert force and so on has affected the daily life and the necessary activities, after the treatment of traditional Chinese and Western medicine is ineffective. 2. 2. The knee joint has “O”-shaped leg or “X”-shaped leg, i.e. knee inversion or knee eversion and other deformation changes. Narrowing of the medial or lateral joint space of the knee joint. 4. Restriction of knee flexion and extension. The angle of flexion or extension of the knee has begun to affect daily life and work. 5, MRI (Magnetic Resonance Imaging) or X-ray film shows severe osteoid formation and destruction of osteochondral bone. 6. Age over 55 years old.