Lying down and feeling the waist topping itself up may be caused by the following reasons: 1. It may be caused by a herniated lumbar disc. In some patients suffering from lumbar disc herniation, often due to nerve root stimulation, resulting in spasm of the lumbar muscles on one or both sides. In some patients with lumbar disc herniation, one or both lumbar muscles may spasm due to nerve root irritation, which may cause the above symptoms to occur when the patient is lying down. 2. Acute lumbar sprain may exist, for example, if the patient has an acute lumbar sprain due to lifting heavy objects, the lumbar muscles on one side may remain under high tension for a long time, which may cause the above sensation when the patient is lying down. 3. 3, this condition may be due to the sacroiliac joint, the lumbosacral region and the hip joint around the relevant lesions, such as sacroiliac arthritis, congenital hip dislocation, ankylosing spondylitis, anterior pelvic tilt and a series of lesions, may be due to the relative relationship between the pelvis and the lumbar spine, and lead to the patient in lying down with the lumbar upward top of the feeling.