Lying down buttock pain standing without pain consider with muscle strain, sacroiliac arthritis, lumbar intervertebral disc herniation and so on. 1. Muscle strain: when lying down the buttock pain may be considered to be caused by hip muscle strain, local aseptic inflammation, lying down the accumulation of lactic acid caused by pain. 2. sacroiliac arthritis: sacroiliac joint degeneration, hyperplasia, narrowing of the joint space, when lying down may also appear buttock pain, pain disappears when standing. 3. Lumbar disc herniation: when lying down due to the mattress is too soft to cause lumbar distortion, lumbar intervertebral discs bear the increased load of the emergence of radiating pain in the buttocks. Lying down buttock pain standing pain may also have other reasons, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor to clarify the cause and treatment.