Chondromalacia patella is a disease characterized by degeneration and degeneration of the patellar cartilage due to strain and trauma, so its formal name should be “chondromalacia patellae”, but the lesion of chondromalacia patellae is not only limited to the patellar cartilage, but the corresponding femoral condylar cartilage is also damaged, so it is more appropriately called chondromalacia patellofemoralis. Patellofemoral chondromalacia and its advanced stage patellofemoral arthritis are common conditions that cause knee pain. Trauma is an important cause of the disease, and acute trauma to the knee, knee impingement injuries, acute dislocation of the patella or accumulation of microfractures can cause chondromalacia patellae. Abnormal patellar position such as high patella, low patella, patellar tilt, patellar subluxation or subluxation can cause abnormal pressure on the patellar cartilage over time, resulting in cartilage chondromalacia degeneration. Although trauma is an important cause of chondromalacia patellae, the underlying cause is poor structure in and around the patella, and trauma is only a predisposing factor, which is also an important reason for the tendency to relapse after treatment. The main symptom of chondromalacia patella is post-patellar pain, which is usually not obvious when walking on a flat road, but is aggravated after squatting, going up and down stairs, going up and down slopes or walking long distances, and some patients show the phenomenon of playing soft legs, which is mainly due to the accompanying synovitis, hyperplastic synovial membrane embedded in the joint space or articular cartilage peeling off the joint surface. Some patients have pain that radiates to the back of the knee because the femoral condylar cartilage is also damaged.