Many people have experienced knee pain, but the causes of knee pain are not well understood by many people. The knee joint is the larger and more complex flexor joint in the body, it is subject to high stress and has a stable yet flexible structure. There are many causes of knee pain, so today we will look at what factors cause knee pain due to knee injury: 1. Fat pad strain The fat pad fills the gap at the front of the knee joint and has the effect of strengthening joint stability and reducing friction. The cause of fat pad strain may be due to trauma or long-term friction causing congestion, hypertrophy and inflammation of the fat pad and adhesions to the patellar ligament, thus limiting knee joint movement. This injury occurs in people over 30 years of age who walk, hike or squat frequently. Patients may feel pain in the knee joint, which is worse when fully extended, but there is no restriction of joint movement. The symptoms are obvious after exertion. Meniscal injury is a common injury in athletes. When the lower extremity is weighted, the foot is fixed, and the knee is slightly flexed, a sudden excessive internal or external rotation of the knee (for example, in volleyball, the player suddenly turns around to save the ball while defending) may cause a meniscal tear. A meniscal injury is characterized by a distinct tearing sensation in the knee, followed by joint pain, limited motion, and walking with a limp. The joint exhibits swelling and slipping sensations and pops when the joint is moved. 3. Traumatic synovitis of the knee joint Damage to the synovium due to factors such as trauma or overexertion will produce a large amount of fluid, which will increase the pressure in the joint, and if not eliminated in time, it will easily cause joint adhesions and affect normal activities. Patients will feel pain, swelling and pressure in the knee joint, and the synovial membrane has a frictional and astringent sound. The most obvious feature of the pain is that when the knee joint is actively and extremely extended, especially when there is a certain resistance to do the knee extension movement, the pain in the lower part of the patella will be increased, and the pain is also significantly increased when it is passively and extremely flexed. 4, osteoarthritis of the knee joint This condition is mostly seen in middle-aged and elderly people, mostly women. Overweight loading is the main cause of the disease. The knee joint will be swollen and painful, and sometimes there will be friction sounds when moving the joint. The knee may have an inversion deformity and be accompanied by medial pain. The knee joint is relatively unstable when it is slightly flexed. If a sudden external force causes valgus or valgus, it may cause medial or lateral collateral ligament injury. Medial collateral ligament injuries account for the majority of clinical cases. In this type of injury, for example, the patient will have a clear history of trauma, pain and pressure on the medial side of the knee, increased pain with passive abduction of the lower leg, swelling on the medial side of the knee, and ecchymosis after a few days. Knee movement will be restricted. 6, improper exercise Some elderly people like to hike, but if they do not prepare for the activity or exercise too much, it can also cause joint pain. Especially people who suffer from synovitis or osteoarthritis, more likely to cause joint disease attacks or aggravation. In mountain climbing, when descending a mountain, the weight of the whole body is placed on one knee joint, and the pressure on the knee joint is several times greater than when standing normally. The same situation occurs when people go up and down stairs. 7, bad walking habits For example, often wearing shoes that do not fit the foot or walking long distances in slippers or high heels, will make the knee joint in an abnormal state of stress for a long time, resulting in chronic damage to the knee joint, causing knee pain.