1.In principle, elderly people over 55 years old with severe bone destruction on knee X-ray, significant pain, standing or walking dysfunction due to joint deformity and/or twinning, instability, and no serious cardiovascular, cerebrovascular, hepatic or renal dysfunction are surgical indications for artificial knee arthroplasty. 2.Primary osteoarthrosis, rheumatoid arthritis, traumatic arthritis and some other non-septic arthrosis in the late stages, the affected side of the joint pain, or walking limp. 3. If the bone tumor of the distal femur or proximal tibia is in a condition to preserve the limb, artificial knee joint replacement with special prosthesis can be performed after resection of the tumor segment. The purpose of surgery is to firstly relieve the pain and secondly to rebuild the stability and mobility of the knee joint. The surgical procedure is determined according to the patient’s condition, age, occupation, weight, and mental status.