The early manifestation is pain in the front side of the knee joint, which is aggravated when going downstairs, and in severe cases, it is often necessary to go downstairs sideways and sideways. It is often misdiagnosed as “rheumatism”. When the disease worsens, it becomes difficult to squat and painful at night, which affects sleep and normal life. In advanced stages, due to severe wear and tear, free bodies may appear in the joint cavity, causing intra-articular strangulation and sudden jamming of the joint. A typical examination reveals a patellar grinding test (+); a sassafras sound. Clinical x-ray examination often shows varying degrees of osteophytes, and x-ray axial examination shows lateral tilting or subluxation of the patella, narrowing of the lateral patellofemoral joint space, and excessive long-term wear and tear of the lateral patellofemoral joint, resulting in subchondral osteochondrosis of the corresponding joint, with “moon bud-like” osteochondrosis seen on lateral x-ray of the patella. Normal patellar image The patellar subluxation or tilt image of chondromalacia patellae: Biological normal patellar image during patellofemoral joint activity, analysis of the mechanics of patellar subluxation or tilt image of chondromalacia patellae, analysis of the pathology of surgical specimens of the disease and combined with years of clinical experience, confirmed that the occurrence of chondromalacia patellae is due to different degrees of patellar subluxation or tilt, as the patella slides on an abnormal trajectory, resulting in poor wear and tear of the lateral patellofemoral joint space. The lateral space of the patellofemoral joint is poorly worn. When the following phenomena occur, patellar chondromalacia should be highly suspected: pain on the anterior side of the knee joint, increased pain when sitting and standing up or going downhill, often with “weak legs, fear of cold joints, or repeated swelling and fluid accumulation in the knee joint.