Pain below the waist may be lumbar sprain, lumbar disc herniation, kidney stone, sacroiliitis, ankylosing spondylitis. 1. Lumbar sprain: It may be caused by strenuous exercise or sudden change of waist from one position to another, resulting in muscle strain or disorder of small joints of lumbar vertebrae. The pain is obvious and you dare not move your waist, and the symptoms can be alleviated by resting. 2. Lumbar disc herniation: because the nucleus pulposus protrudes and compresses the nerve root, edema and aseptic inflammation appear, so there will be pain in the lower back, and some of them also have leg pain and numbness, which can be clearly diagnosed by lumbar spine MRI film. 3. Kidney stones: manifested as pain on both sides below the waist, the pain is severe and sudden, accompanied by abnormal urination, which can be clearly diagnosed through renal ultrasound. 4. Sacroiliac arthritis: mainly manifested as lower back pain, morning stiffness, joint mobility disorder. 5. Ankylosing spondylitis: aggravated after sitting for a long time or in the morning, and can be alleviated by appropriate activities. The pain is obvious at night. So if the pain below the waist is more intense, rest does not get better need to go to the hospital to check.