I often see patients with knee pain in the clinic, so what causes knee pain? I believe there are several causes of knee pain: 1. Infection, including septic infection, special infections such as tuberculosis, brucellosis, typhoid, etc. 2. Metabolic diseases such as gout, tumors of the knee joint, etc. 3. Structural damage to the knee joint itself, such as ligament, meniscus damage, fractures, bone contusions, articular cartilage damage, etc. 4. Degenerative diseases of the knee joint Osteoarthritis is caused by degeneration of the articular cartilage. Roughly divided into these categories, if you knee pain with fever, swelling to consider whether it is an infection or gout. If it is after a slip or injury consider if it is a ligament, meniscus, cartilage or minor fracture of the knee. If the knee is painful after sitting or going up and down stairs, consider whether it is osteoarthritis. That is why the necessary laboratory tests are essential: blood count, sedimentation, C-reactive protein, blood uric acid. Necessary tests: positive and lateral knee films, MRI of the knee.