Left knee pain when walking is common for several reasons: first, osteoarthritis of the knee joint, knee joint surface cartilage damage after rough and uneven, in flexion and extension activities will lead to abrasive pain symptoms, while cartilage debris can also stimulate the synovial membrane causing secondary synovitis resulting in joint effusion, swelling and pain symptoms. Mild arthritis can be treated conservatively with drugs such as oral loxoprofen sodium and microwave therapy, which can relieve joint pain. Moderate arthritis usually requires arthroscopic surgery to remove inflammatory synovial membrane to repair articular cartilage damage, while severe arthritis requires consideration of artificial joint replacement surgery. Second, knee meniscus injury, knee meniscus injury by the femur and tibial plateau double extrusion, can cause joint pain symptoms, symptoms can also be accompanied by joint interlocking, meniscus injury usually requires arthroscopic surgery to repair.