Artificial knee surface replacement has become a common clinical procedure to address severe knee pathology, so what kind of patients are suitable for this procedure? Simply put, artificial knee surface replacement surgery is used for patients with severe knee pain, limited motion, with or without significant deformity, who have failed to respond to conservative treatment or whose results are not significant. First, a brief introduction to the procedure is that an artificial knee surface replacement is a procedure that replaces the damaged knee joint with an artificial knee joint (also known as an artificial prosthesis), the so-called surface replacement is simply replacing the “joint surface” of the knee joint. The “surface” of the knee is replaced, while most of the bone and ligaments surrounding the knee joint are retained. Therefore, the artificial knee surface replacement mainly addresses the disease of joint surface destruction, while the major bones that make up the joint and the ligaments around the joint must be normal. Severe destruction of the bone such as bone tumors and joint instability due to severe damage to the joint ligaments preclude this procedure. Since the life expectancy of the artificial knee is limited, averaging about 20 years, we recommend that surface replacement of the artificial knee be performed after the age of 60, based on an average life expectancy of 80 years. Premature artificial knee surface replacement surgery may face the problem of joint revision during one’s lifetime. Here are a few common diseases 1, osteoarthritis, also known as osteoarthritis, osteoarthrosis, degenerative arthritis, hypertrophic arthritis, also often called osteophytes, bone spurs, is a common chronic disease of the knee joint, but also the most commonly used artificial knee surface replacement. The main lesion of this disease is the destruction of articular cartilage and secondary osteophytes. The main clinical manifestations are joint pain and inflexibility, characterized by pain during activity (e.g., walking) and in severe cases significant joint deformation and loss of walking function. x-rays show narrowing of the joint space, subchondral bone sclerosis and cystic changes, and lip-like osteophytes at the joint edges. Osteoarthritis represents the aging of the joints, but in fact, all organs in the body do not “age” at the same time. If the knee joint is aging prematurely, but other organs are functioning well, this is the best indication for surface knee replacement. Early osteoarthritis can be treated with a combination of activity restriction, oral medications, joint cavity injections, and physical therapy, while late stage conservative treatment is not effective and requires an artificial knee surface replacement. As the name implies, traumatic arthritis refers to joint damage secondary to knee injury, mostly due to damage to the cartilage, meniscus, and ligaments of the joint surface, resulting in uneven or collapsed joint surfaces, joint instability, and abnormal force lines, resulting in uneven stress on the joint surface and early joint destruction. The age of onset of traumatic arthritis is younger than that of osteoarthritis, therefore, early artificial knee surface replacement surgery is not advocated, but rather conservative treatment or minimally invasive surgery should be used first, and only those with severe joint surface destruction in late stages should undergo artificial knee surface replacement surgery. Rheumatoid arthritis Rheumatoid arthritis is a medical disease (rheumatology), a chronic systemic autoimmune disease characterized by synovial lesions, which can lead to destruction of joint cartilage and bone, joint dysfunction and even disability as the disease progresses. Rheumatoid arthritis mainly affects the small joints of the hands, but the knee joint is sometimes involved. Artificial knee surface replacement mainly addresses patients with advanced rheumatoid disease, whose knee joints have been significantly deformed and have severe dysfunction. 4, ankylosing spondylitis ankylosing spondylitis is a younger disease than rheumatoid, once called “central rheumatoid” meaning that the spine and large joints are mainly involved. The manifestation of ankylosing spondylitis in the knee joint is that the joint is straight and fixed in a deformed position, which can severely affect activities of daily living. In the early stages of ankylosing spondylitis, the main treatment is internal medicine. In the late stages, if the joint is straightened in a deformed position and the quality of life is seriously affected, artificial knee surface replacement surgery can be performed. 5, other hemophilic arthritis, joint surface destruction can be artificial knee surface replacement surgery in the case of effective replenishment of coagulation factors; pigmented villous nodular synovitis, severe pain joint surface destruction can be artificial knee surface replacement; septic arthritis and joint tuberculosis, joint surface destruction serious patients in the infection or tuberculosis control after 2 years, can also be artificial knee surface replacement surgery. Knee surface replacement surgery can also be performed after 2 years of infection or tuberculosis control. To summarize, surface arthroplasty is primarily a treatment for joint surface destruction, while most of the bone and ligaments around the joint must be normal. Because of the longevity of the artificial joint, it is not recommended to perform an artificial knee surface replacement before the age of 60, although this is not absolute and we do not mechanically wait until after the age of 60 if the patient has severe knee damage and no other better treatment is available. The surgery is primarily for knee pain, but also for deformity and limited motion, but joint instability and weakness are not indications for surface knee replacement. However, it is important for patients to be aware of the fact that they cannot run, jump or squat completely after surgery. In addition to surface knee replacement, there are also hinged knee replacements and unicondylar replacements, which have different indications for surgery and will be described at a later date.