What kind of pain requires a doctor’s visit? 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 it is time to determine the level of pain as well as the level 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 the ground pain (especially clear pain in the inner or outer knee joint gap), cross-locking (the knee joint suddenly stuck, need to move or other people’s help in order to unlock), we need to consider meniscus or cartilage injuries, prompt medical attention.