Anterior knee pain is a common condition that many people consider to be a sequelae of arthritis or injury, but patellar instability is often overlooked, even by non-sports medicine medical professionals. Patellofemoral instability is a common cause of anterior knee pain, a common disorder of the patellofemoral joint, and an important cause of chondromalacia of the patella or osteoarthritis of the patellofemoral joint. Advances in biomechanics and imaging technology, as well as the diversification of clinical detection methods, have led to the gradual recognition that degenerative changes in the patellofemoral joint are mostly due to patellar instability caused by poor patellofemoral joint fit or patellar force line malalignment, such as patellar deviation, patellar tilt, patellar elevation, patellar subluxation, etc. The main manifestations: (1) Pain is the most common symptom, usually not constant in nature, but its location is in the anterior knee area, with the anterior medial knee being the most common. The pain can be aggravated by excessive activity, especially when going up or down stairs, climbing or prolonged flexion and extension activities. (2) The “weak leg” is a momentary weakness and instability of the knee joint when walking with weight, and sometimes the patient may even fall. This phenomenon is often due to weakness of the quadriceps muscle, or due to the patella slipping out of the intercondylar groove due to subluxation. (3) Pseudo-embolism is a momentary involuntary restriction disorder that occurs during knee extension. This phenomenon often occurs when the weight-bearing knee joint slides into the intercondylar groove from flexion to extension, and is often clinically distinguished from true impingement caused by a meniscal tear or displacement of the strangulation or free body. Treatment: 1. Non-surgical treatment (1) Restriction of activities Restriction of certain activities in the patient’s daily life, such as climbing, climbing, etc., can reduce the load on the patellofemoral joint and reduce patellofemoral joint wear, especially when it is understood that a certain activity is significantly related to the aggravation of symptoms, the use of restriction of this activity can achieve the purpose of improving symptoms. (2) Quadriceps exercises Subacute or chronic cases are often accompanied by significant quadriceps atrophy and muscle strength reduction, especially the weakening of the medial femoral oblique head muscle strength, which can further aggravate the instability of the knee joint, causing joint swelling and worsening symptoms, therefore, quadriceps exercises should be strengthened to improve the muscle strength ratio of the quadriceps and N cord. (3) Brace treatment The patellar brace has the function of limiting and stabilizing the patella, it is used for acute patients or when participating in a certain sport or more activities. Long-term wear can cause local discomfort and lead to atrophy of the quadriceps muscle. (4) Drug treatment Non-steroidal anti-inflammatory drugs can reduce the symptoms of osteoarthritis in the patellofemoral joint. Other treatments are not significant. 2.Surgical treatment If the patient’s symptoms are obvious and the conservative treatment mentioned above is not effective, surgical treatment can be considered. There are many surgical methods, at present, the main use of minimally invasive technology for ligament release and reconstruction, the surgery is less traumatic and satisfactory recovery.