Many people are unfamiliar with this name, but this disease is not uncommon in the population. Many people are accompanied by other injuries, which are addressed together with the treatment, but this disease is characterized by the difficulty of diagnosis, but the pain is still quite uncomfortable, so it is still important to pay attention to it. It is also called infrapatellar fat pad injury or infrapatellar fat pad inflammation and Hoffa syndrome. The normal human infrapatellar fat pad is wedge-shaped, located in the space between the femur, tibia and patellar tendon, covered by synovial membrane, has a cushioning and lubricating effect. 1, cause of injury: under normal circumstances the subpatellar adipose tissue plays a good role in moving with the patella during knee flexion and extension, but if too much fat is deposited in the fat pad or if the quadriceps muscle tone is reduced, or if the knee recoils, it is possible to jam the fat pad in the joint space, causing pain and swelling of the joint. Causes of fat pad enlargement include: trauma, strain, occupational lesions, etc. Long-term repeated swelling and compression can eventually damage the articular cartilage and cause joint inflammation. 2, clinical manifestations: mostly seen in women, young and middle-aged people, especially those who often go up and down the stairs or squatting, walking is common. Soreness and weakness in the front and lower part of the knee joint, generally without sharp pain, can also be fixed when the joint flexes and extends to a certain angle of soreness, pain is located behind the upper end of the patellar ligament and its sides, sometimes can be radiated to the N fossa. There is no obvious obstacle to joint movement; the symptoms can be aggravated after activity and relieved after rest, and the pressure pain is obvious under the patella and on both sides of the patella. Treatment: If the symptoms appear only occasionally, conservative treatment can be preferred, mainly with quadriceps muscle training, physical therapy, massage, wearing knee pads, etc. Topical medication can also be chosen to avoid excessive stairs and strenuous exercise. If the symptoms recur and there is significant swelling of the joint, surgery is feasible. Arthroscopic surgery can solve the problem quickly and effectively; however, if long-term failure to deal with the problem causes damage to the articular cartilage, the symptoms may still occur even after surgery, as the damaged cartilage cannot be regenerated.