Lying on the waist to consider the lumbar vertebrae physiological curvature increased or lumbar spondylolisthesis, anterior pelvic tilt, buttock muscular development, etc. . 1. Lumbar spine physiological curvature increase: normal lying down when the waist and bed can be attached together, or a slight gap, if the waist hanging, consider lumbar spine physiological curvature, this is because of the usual sedentary or posture caused by poor erector spinae muscle strain spasm, or spasm of the adductor muscle pulling the spine, so that the physiological curvature of the changes in the case is prone to sedentary lumbar pain, rest to alleviate. 2. Lumbar spondylolisthesis: mostly occurring in the elderly and lumbar isthmus cleft people, lumbar spine forward displacement, resulting in lumbar back depression, lying down when the waist hanging. 3. Anterior pelvic tilt: due to body posture, the physiological curvature of the lumbar spine becomes larger, and the anterior pelvic tilt lumbar space is large. 4. Muscular buttocks: the buttocks protrude, there will also be lying waist hanging pain. There are many reasons for lying down with a hanging waist, if the combined discomfort, we should consult the doctor in time, take a lumbar spine front and side view film to see if there is any abnormality in the lumbar spine.