Leg joint pain may be caused by ligament injury, meniscus injury, osteoarthritis, rheumatoid arthritis and so on. 1. Ligament injury: due to strenuous exercise or traumatic violence and other factors lead to ligament area tear or rupture injury, often cause obvious joint pain and activity limitation, and accompanied by knee swelling and skin bruising. 2. Meniscus injury: mostly due to physical exercise or traumatic fall, resulting in the integrity and continuity of the meniscus is damaged, meniscus injury can cause knee pain, swelling and limited movement. 3. Osteoarthritis: Degenerative lesions of the knee joint can lead to osteoarthritis, resulting in wear and tear of the cartilage of the knee joint, joint effusion and other phenomena, resulting in knee joint pain, swelling, weakness, and even restriction of activities and other symptoms. 4. Rheumatoid arthritis: mainly an autoimmune disease with erosive arthritis as the main symptom, cold, humidity, exertion and other factors can trigger pain and swelling in the joints. Leg joint pain may also be caused by other reasons, the patient should go to the hospital in time to identify the cause of treatment under the guidance of the doctor.