Elbow and knee pain may be due to gouty arthritis, rheumatoid arthritis, ankylosing spondylitis and degenerative arthritis. 1. Gouty arthritis: The attacking joints are mainly in the lower limbs, causing redness, swelling, heat and painful inflammation. The first attack occurs most often in the first toe joint, followed by the ankle and knee. Most attacks occur in the middle of the night, after eating a large meal or drinking a lot of alcohol, resulting in severe pain and inability to walk. 2. Rheumatoid arthritis: It is a multi-system disease that mainly affects the joints, leading to fever, swelling and pain, and the pain and stiffness tend to worsen after rest. Therefore, the morning is the time when the pain is most severe. It most often involves the wrists and hands involving the same joints on both sides of the body and may also affect other parts of the body. 3. Ankylosing spondylitis: mainly produces inflammation of the joints and tendons, especially in the pelvis and spine, and is accompanied by damage to the bone marrow and edema. Chronic spinal pain and stiffness are common at first, followed by ossification, which leads to progressive stiffening of the joints, and onset of the disease before the age of 18 years, often resulting in painful enlargement of the joints of the extremities, especially the knees. 4. Degenerative arthritis: After the wear and tear of cartilage in the joints, the peripheral bone proliferates abnormally and the joint cavity narrows, which makes the joints painful and unable to move fully. It is more common in the joints of the lower limbs that are subjected to greater pressure, such as knees, femurs, hips, ankles and other joints, as well as the joints of the hands or feet that are frequently moved.