Teenagers’ knee pain may be caused by a large number of sports, or it may be caused by other diseases such as synovitis, meniscus injury, osteoarthritis and so on. 1. A lot of sports: when teenagers have the symptom of knee soreness, it may be that they have played a lot of sports for a long time in their daily life or training, and the local lactic acid builds up, which leads to the phenomenon of knee joint pain. 2. Synovitis: Synovitis is usually caused by infection, trauma, immunity and other factors, which will cause swelling, pain, limited joint movement and other symptoms, and also accompanied by fever, elevated temperature and other symptoms. 3. Meniscus injury: Meniscus injury is caused by various factors such as indirect violence or long-term weight-bearing cumulative injury. The main symptoms are knee pain, swelling, joint popping, interlocking joints, etc., and there may also be knee pain. 4. Other: Osteoarthritis, rheumatoid arthritis and other diseases may also cause knee pain in teenagers. Teenage patients with symptoms of knee pain should seek timely medical treatment and follow the doctor’s instructions for standardized treatment.