“The most common symptom is pain around the kneecap (patella), also known as “patellofemoral joint pain syndrome”. In addition to running, prolonged walking, cycling, jumping and other sports that require repeated knee flexion can also cause “runner’s knee” symptoms. I. What are the causes of “runner’s knee”? 1. Excessive exercise. Long distance running such as marathons; activities that can significantly increase the stress on the patellofemoral joint such as climbing and lunging. 2. Iliotibial bundle friction syndrome. The iliotibial bundle is the lateral strip ligament of the knee joint. Excessive friction between the iliotibial bundle and the lateral bone surface of the femur during running leads to inflammation of the ligament or bursa. 3. Knee joint trauma. Such as knee injuries caused by falls, impacts, sprains, etc. Trauma to the knee is likely to cause meniscal or ligament damage, so if swelling, pain and restricted movement persist after trauma, it is important to visit a hospital to rule out structural damage to the joint. 4. Developmental abnormalities. Abnormal force lines in the lower extremities, such as “O” leg or “X” leg, can lead to uneven stress on the cartilage of the knee joint, and the cartilage is prone to wear and tear in areas where stress is concentrated, resulting in injury and pain. The patella and femoral trochlea have “convex” and “concave” articular surfaces, respectively. If the patella becomes shallow, flattened, or even “convex”, the patella will be tilted and the stress on the articular cartilage will be uneven; in severe cases, the patella can be dislodged from the femoral pulley track, called patellar dislocation. 5, foot problems. Foot inter-articular activity is too large or flat feet and other cases, the foot falls to the ground when the cushioning effect of ground recoil is reduced, so that the knee joint is subjected to excessive stress. 6, weak or unbalanced muscle strength. The normal activity trajectory of the patella is controlled by the collaboration of various groups of muscles in front of the thigh, if the muscle strength is weak or unbalanced between the muscles, it will lead to uneven force on the patella, and wear and pain will occur in the parts that are overstressed. Second, what are the symptoms of “runner’s knee”? 1. Pain around the kneecap, especially in the area of contact between the kneecap and the femur at the back. 2. The pain increases when the knee is flexed, and increases when walking up or down stairs. 3. Swelling of the knee joint. 4. Popping or rubbing sensation in the knee joint. III. How to treat? Most mild to moderate symptoms will resolve on their own after a certain period of rest, except for structural damage within the joint. The following methods can help speed up recovery: 1. Reduce the amount of exercise and minimize weight bearing on the knee joint. Some sports fans insist on exercising even after the knee joint becomes painful and uncomfortable, which is not conducive to joint recovery. 2. Apply ice to reduce joint pain and swelling for 20-30 minutes each time, more than 3 times a day, for 2-3 days, or until the pain disappears. 3.Elevate the affected limb to help reduce swelling. 4. Take oral anti-inflammatory and analgesic drugs, such as Cilpro and Fotarim, which help to reduce swelling and pain. Patients with gastrointestinal problems such as gastric ulcer should use with caution and long-term use is not recommended. 5.Intra-articular injection of lubricants such as hyaluronic acid and gibberellic acid has a certain effect on increasing cartilage nutrition and inhibiting inflammation. 6, lower limb muscle strength training, especially the training of the quadriceps. 7.When you have flat feet, you can wear orthopedic insoles to elevate the arch of the foot. 8.If the symptoms of joint swelling and pain and restricted movement persist, you need to go to the hospital to rule out structural damage to the joint, such as meniscus, ligaments, cartilage damage may require surgery, most of the current joint surgery can be completed under arthroscopic minimally invasive operation, post-operative recovery is fast and has little impact on function. 9, rehabilitation time varies from person to person, when the knee joint in a variety of activities are no pain symptoms can gradually resume sports, do not rush to resume sports before rehabilitation, otherwise it can cause permanent damage to the joint. Fourth, how to avoid “runner’s knee” appear? 1. Exercise regularly to strengthen your muscles. 2. Wear orthopedic insoles if you have flat feet. 3, select the right sports shoes, timely replacement of deformed, loss of support of sports shoes. 4.Avoid running on hard ground, such as running on concrete. 5.Maintain the appropriate weight. 6.Do not suddenly increase the intensity of exercise, but slowly increase the amount of exercise.