On 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. Zhen Dong, Department of Sports Medicine, Guizhou Orthopaedic Hospital ③There were no very obvious changes in patellar and pulley degeneration on the x-ray. ④ There was no abnormal patellofemoral joint relationship, such as obvious patellar subluxation. 2, The magnetic resonance imaging (MRI) confirmed that there were no obvious problems with the intervertebral compartments and the cartilage of the patellofemoral joint other than the intervertebral compartment with painful knee joint destruction. 3, After intraoperative arthroscopic exploration all other parts of the knee joint except the damaged interval are clear. Only when the above three conditions are met can the unicondylar replacement be performed, otherwise the other problematic parts of the knee that are not replaced will still be painful after the unicondylar replacement. This will lead to unsatisfactory surgical results.