I often hear people complaining of pain in the front of their knee, which is especially noticeable when walking up and down stairs. This phenomenon may be caused by chondromalacia patellae. The patella is triangular in shape, located in front of the knee, and is the main fulcrum of the lower limb straightening muscles, forming the patellofemoral joint with the femur, which plays a role in protecting the knee joint. When the patella is softened, the force of lower limb straightening is weakened or disappears, and the knee joint is not protected in time, which will manifest as weakness of the thigh and knee pain, which is only sore at the beginning of the activity and feels comfortable after the activity. If the activity is increased for a longer period of time, the pain increases significantly and is relieved after rest. After a long period of time, quadriceps muscle atrophy, thigh thinning, and swelling of fluid in the knee joint may occur. The prevention and treatment of chondromalacia patellae can generally take the following four methods: First of all, knee rehabilitation training can be used. Do not over-activate the knee joint, and try to avoid knee extension and flexion activities and semi-squatting posture during weight-bearing. Strengthen the functional exercise of the quadriceps, such as lying flat on the bed, straightening the knee joint and repeatedly lifting the lower limb. Rehabilitation is a specialized discipline, and the doctor needs to know the target according to the needs of the condition. Secondly, patients can do ultrasonic physical therapy and topical pain relief creams to reduce intra-articular pressure, improve local blood circulation and promote trauma repair. Thirdly, intra-articular injections can be performed to apply some drugs to improve intra-articular symptoms. However, not all patients are suitable. Fourth, arthroscopic surgery treatment. Arthroscopy is a minimally invasive treatment, which means that 2-3 small one-centimeter holes are made in the knee joint and special instruments are used to perform intra-articular operations to treat intra-articular diseases. It is suitable for: patients who have had poor results with quadriceps exercises, medication and joint injections; patients with cartilage damage of more than 2° or cartilage damage of 2° but with a large area of damage; patients with combined osteoarthritis of the knee and other diseases of the knee; patients who require restoration of knee function as soon as possible or require maximum restoration of knee motion function because of work and sports needs.