A lying down on the waist pain consider lumbar disc herniation, lumbar back musculoskeletal inflammation, lumbar spine fracture, osteoporosis and other reasons. 1. Lumbar disc herniation: Because the nucleus pulposus protruding from the degenerated lumbar intervertebral discs protrudes through the ruptured annulus fibrosus and presses on the nerve roots, when lying down due to the mattress is too soft and the posture is not good, resulting in the nerve compression is serious, and lumbar pain occurs. 2. Lumbar dorsal myofasciitis: it is because of the aseptic inflammation of fascial tissues, resulting in local adhesion, lumbar spine stiffness and activity limitation. 3. Lumbar spine fracture: there is a history of lumbar spine trauma, lumbar spine pain, aggravated by lying down, and activity limitation. 4. Osteoporosis: mostly occurs in the elderly, can appear lying back pain. Once lying down waist pain need to go to the hospital to check, also need to exclude lumbar spine bone tumor and other diseases, it is recommended to clarify the cause of treatment.