Under the premise of being suitable for joint replacement, unicondylar knee replacement can be performed if the following conditions are met: 1. There is no problem in checking patellofemoral closure: (1) The patient’s knee joint is not tender or painful when going up and down stairs or squatting. (2) The pressure patellar test, grinding patellar test, patellar rim acupressure pain and knee extension resistance pain on examination are negative, or the pain is very mild. (3) There were no very obvious changes in patellofemoral and pulley degeneration on X-ray. (4) There is no abnormal patellofemoral joint relationship, such as obvious subluxation of the patella. (2) Magnetic resonance imaging (MRI): confirmed that there were no significant problems with the intervertebral compartments and cartilage of the patellofemoral joint other than the intervertebral compartment with painful knee destruction. 3. After intraoperative arthroscopic investigation, all other parts of the knee joint except for the damaged interval are clear: unicondylar replacement can only be performed if the above three items are met, otherwise the other problematic parts that are not replaced will still be painful after unicondylar replacement. This will lead to unsatisfactory surgical results.