Many people in my specialty clinic have knee osteoarthritis, knee degeneration, bone spur growth, and narrowing of the knee joint space. The main clinical symptoms are knee pain and impaired mobility, with pain predominantly when descending stairs, and in severe cases also when walking on a level surface. There are many kinds of methods for knee osteoarthritis and knee degeneration, including medication, Chinese herbal medicine treatment, massage rehabilitation, surgery and so on. If the pain is unbearable and the knee joint space is narrowed, then artificial knee replacement can be performed. At present, this surgery is very mature, and all major hospitals in China will perform this surgery, but at present, the most common surgery done in China is total knee replacement. Simply put, it is to replace both the inside and outside of the knee joint, but many patients have a good outer gap and a narrow inner gap. In this case, we usually choose to keep half of the patient’s knee joint, and replace the narrow side of the knee joint, which is called unicondylar knee replacement. Compared to total knee replacement, unicondylar replacement is less invasive and the incision is smaller. Most importantly, it also preserves half of the patient’s own knee. Regardless of the procedure, the patient starts walking on the ground on the second day after the surgery, and the patient’s knee function usually returns to normal on the fifth day after the surgery. My two cases, to demonstrate the first patient, female, 60 years old, knee pain, medial and lateral gap narrowing, in our hospital for total knee arthroplasty The second patient. The second patient is a 62-year-old woman with knee pain, which is obvious when she goes down the stairs. The lateral knee joint clearance is fine, but the medial knee joint is narrow, so we gave her a medial knee replacement, which is a unicondylar replacement. The first patient, total knee arthroplasty, preoperative and postoperative as follows: