Knee pain after running may be related to the following reasons: 1. It may be due to the damage inside the knee joint caused by running. If the patient does not exercise or does not know how to exercise, the meniscus, cartilage, ligaments and other parts of the knee joint may be damaged during the running process, resulting in knee pain after running. 2. It may be caused by aseptic inflammation of the knee joint. This is often seen when the patient has a cold knee joint during or after running, which leads to internal inflammation and pain. 3. It may be caused by excessive wear and tear of the knee joint, which is often seen in elderly people or patients who are overactive. The overuse of the knee joint leads to excessive wear and tear of the cartilage or bone inside the knee joint, resulting in osteoarthritis, which may cause severe pain after running. 4, this situation may also be caused by excessive fatigue of the knee joint, for example, patients do not exercise in the past, suddenly exercise due to the lack of muscle strength around the knee joint, very easy to cause fatigue of the ligaments and muscles of the knee joint The knee joint pain can occur after running.