Knee pain bending and straightening pain may be caused by osteoarthritis, synovitis, meniscus injury and other causes. Patients can be treated with drugs that nourish cartilage, non-steroidal anti-inflammatory drugs and arthroscopic synovectomy and arthroscopic synovectomy. 1. Osteoarthritis: If the patient has osteoarthritis caused by dislocation, fracture or other structural injuries around the joints, which leads to the symptoms of knee pain bending and straightening pain. You can take glucosamine hydrochloride capsule, glucosamine sulfate capsule and other drugs that nourish the cartilage to relieve the pain. 2. Synovitis: Synovitis can be caused by acute and sudden trauma resulting in joint injury, or because of long-term joint fatigue, stimulating the synovial membrane, so that the synovial membrane thickening and inflammation, resulting in knee pain bending and straightening pain phenomenon. Indomethacin enteric-coated tablets, ibuprofen extended-release capsules and other non-steroidal anti-inflammatory drugs and arthroscopic synovectomy for treatment. 3. Meniscus injury: due to overloading of the knee joint or various acute and chronic injuries triggered by the meniscus injury, the knee pain will appear bending and straightening pain phenomenon. It can be treated by resection and arthroscopic surgery. When patients have knee pain bending and straightening pain, they should go to the regular hospital for treatment in time to help screen the cause of the disease. Do not use medication on your own, and follow your doctor’s instructions.