Knee can not bend, a bend will have pain symptoms, commonly due to osteoarthritis of the knee, meniscal damage and other reasons, as follows: First, osteoarthritis of the knee: most elderly patients with osteoarthritis of the knee, advanced joint massive osteophytes, joint movement is limited, bending will lead to bone impact caused by joint pain, pain is usually more intense, the patient walking will also be limited, X-ray X-rays can reveal osteophytes in the knee joint and narrowing of the joint space; second, meniscus injury: young patients may have meniscus injury, after tearing the meniscus of the knee joint, stimulation of the meniscus injury site when bending the knee joint will lead to knee pain symptoms, and at the same time, symptoms of knee joint interlocking may occur, and the range of motion of the knee joint will be restricted. MRI can reveal the site and extent of the meniscal injury. In addition, surgical treatment can provide complete relief of both of these lesions.