There are many causes of knee pain, including osteoarthritis of the knee joint, ligament injury, meniscus injury, synovitis and so on, all of which can cause knee pain. 1. Osteoarthritis of the knee: it is one of the most common causes of knee pain, which is due to the degeneration of articular cartilage after repeated wear and tear, resulting in osteophytes, joint cavity effusion caused by pain and swelling of the knee, and limited activities. 2. Ligament injury: knee ligament injury is often caused by trauma. Ligament injuries often cause pain and limitation of movement in knee arthritis. 3. Meniscus injury: Meniscus injury of the knee joint will cause pain in the knee joint, cardiovascular problems and limited movement. 4. Synovitis: Synovitis is one of the most important causes of knee swelling and pain. If you have knee pain, you should go to a regular hospital for consultation and treatment, and do not take care of it by yourself, so as not to delay the condition.