Joint pain in the legs may be caused by osteoarthritis, autoimmune diseases and so on. 1. Osteoarthritis: the joints of the lower limbs are mainly composed of large joints such as hip joints, knee joints and ankle joints as well as many small joints. Due to the effect of gravity, the joints of the lower limbs belong to the load-bearing joints, and the degenerative changes in the joints caused by various reasons will lead to the degeneration of the articular cartilage and osteophytes, which will result in the manifestation of joint pain. 2. Autoimmune diseases: autoimmune diseases may also lead to the above symptoms, such as rheumatic and rheumatoid diseases, which may lead to synovial hyperplasia, narrowing of joint space, etc., involving the corresponding large and small joints, resulting in pain; hyperuricemia leading to gout, which will lead to uric acid deposition in the joints, and may also lead to pain symptoms. Sometimes the cause of leg joint pain cannot be accurately determined by the symptoms alone, and it is necessary to combine the characteristics of the medical history and other test results to make an accurate judgment, and it is recommended to clarify the cause of the disease under the guidance of a doctor.