First, is there obvious trauma to the knee? Pain that is accompanied by obvious trauma must be treated promptly. If there is no obvious trauma, then you need to determine the level of pain and the degree of swelling in the knee. Severe pain with localized swelling must be treated. If the pain is due to sprain: 1, knee sprain pain is slight, no swelling is a mild acute sprain, rest for 3 to 7 days can improve. 2, knee sprain with pain, but also can move or walk, generally belong to moderate acute sprain. The specific degree of injury can be judged according to the swelling after the injury. First, the swelling within a few hours after the injury, this is generally combined with knee ligament injury or joint capsule tear. The second is swelling the day after the injury, which is usually a meniscus or cartilage injury. Thirdly, there is no swelling after the injury, but swelling occurs after pain relief and activity. The fourth is slight swelling after the injury, usually due to mild joint capsule damage. The first three cases are required to consult a doctor as soon as possible, the last one can rest, after the disappearance of symptoms normal activities. 3, knee sprain severe pain, immediate inability to move or dislocation, swelling within a few hours after the injury is obvious, belongs to the severe acute sprain. These need to see a doctor as soon as possible, some patients can also insist on walking after the injury, and even gait is normal, also need to consult a doctor in time. Such injuries generally include: large ligaments such as the medial patellofemoral ligament, anterior and posterior cruciate ligaments and other tears, meniscus tears, cartilage fractures and even tendon ruptures. 4, can’t run fast, can’t turn sharply and stop sharply, one-legged jump difficulty, can’t finish the movement before the injury, these cases belong to chronic sprain, need to consider ligament rupture, patellar subluxation injury or bony structural injuries, need to consult the doctor in time. 5, painful popping of the knee joint (clicking sound), walking on level ground pain (especially clear pain in the inner or outer space of the knee joint), cross-locking (knee joint suddenly stuck, need to move or other people’s help in order to unlock), you need to consider meniscus or cartilage injuries, timely medical attention. Causes of knee pain: 1, fat pad strain The fat pad fills the gap in the anterior part 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 caused by fat pad congestion, hypertrophy and inflammation, and patellar ligament adhesion, thus limiting the activities of the knee joint. This injury occurs in people over 30 years of age who walk, hike, or squat a lot. Patients will feel knee pain, pain aggravated by full extension, but the joint activities are not restricted, symptoms are obvious after exertion. 2, meniscus injury meniscus injury is a common injury in athletes, in the lower limb weight-bearing, foot fixed, the knee joint slightly flexed, if the sudden excessive internal rotation knee extension or external rotation knee extension (for example, volleyball sports, players in the defense, suddenly turn around the fish to save the ball action), may cause meniscus tear. A meniscus injury is characterized by a noticeable tearing sensation in the knee, followed by joint pain, limited mobility, and walking with a limp. The joint shows swelling and slipping sensation, and there is popping sound when the joint moves. 3.Traumatic synovitis of the knee joint The synovium of the knee joint is one of the main structures that make up the knee joint. Synovial cells secrete synovial fluid, which can keep the articular cartilage surface slippery and increase the range of joint activities. Damage to the synovium due to factors such as trauma or overstrain will produce a large amount of fluid, which increases the pressure in the joint, and if not eliminated in time, it will easily cause adhesions in the joint, which will affect normal activities. The patient will feel the knee joint pain, swelling, pressure pain, synovial membrane has friction astringent sound. The most obvious feature of the pain is that when the knee joint is actively and extremely straightened, especially when there is a certain resistance to do the knee extension movement, the pain in the lower part of the patella will be aggravated, and the pain will also be obviously aggravated when the knee joint is passively and extremely flexed. 4, osteoarthritis of the knee joint This disease is mostly seen in middle-aged and old people, mostly women. Overweight load is the main cause of the disease. The knee joint will be swollen and painful, and sometimes there will be friction sound when moving the joint. The knee may appear inversion deformity and accompanied by medial pain. 5, knee ligament injury The stability of the knee joint is relatively poor when it is slightly flexed, if it is suddenly subjected to external force resulting in external or internal rotation, it may cause injury to the medial or lateral collateral ligament. 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, with pain and tenderness on the medial side of the knee, pain that increases when the calf is passively abducted, swelling on the medial side of the knee, and petechiae that appear after a few days. Knee activities will be limited. 6, improper exercise Some older people like hiking, but if they do not do a good job of preparatory activities or too much exercise, can also cause joint pain. Especially those who suffer from synovitis or osteoarthritis are more likely to cause joint disease attacks or aggravation. In mountaineering, when going downhill, the weight of the whole body is completely added to one side of the knee joint, and the pressure on the knee joint is several times that of normal standing. When people go up and down the stairs, the same situation will occur. 7, bad walking habits, such as often wearing ill-fitting shoes or wearing slippers, high-heeled shoes walking long distances, will make the knee joint for a long time in a non-normal state of stress, resulting in chronic knee injury, causing knee pain. 9, rheumatism, rheumatoid, ankylosing spondylitis, lupus erythematosus and other immune diseases caused by knee joint lesions. 10, metabolic diseases such as “gout” caused by the incidence of knee pain has a significant upward trend.