The buttocks are medically known as the hips, and there are many reasons for soreness and swelling of the buttocks, the common ones being pyriformis syndrome, lumbar disc herniation, sacroiliac arthritis, and so on. 1. Piriformis syndrome: the sciatic nerve is compressed in the region of the piriformis muscle, which mainly manifests as soreness and pain in the buttocks, radiating along the sciatic nerve to the calf and foot. Painful claudication may occur when the pain is severe. 2. Lumbar disc herniation: the protruding nucleus pulposus compresses the peripheral nerves, which may cause abnormal function of the sensory nerves in the buttocks, resulting in soreness and swelling of the buttocks. 3. Sacroiliac arthritis: unilateral or bilateral inflammatory reaction of sacroiliac joints caused by various reasons, prolonged standing, running, etc. can induce persistent dull pain, soreness and swelling of the lower back, which can also occur in the buttocks, groin and other parts of the body, and can be relieved after rest. Hip soreness may have other causes such as long-term bad posture, strenuous exercise leading to lactic acid accumulation, femoral head necrosis, etc. It is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and standardize the treatment under the guidance of the doctor.