Lower back does not hurt when standing but hurts when bending down is related to lumbar disc herniation, strain of the lumbar muscles, lumbar sprain, and so on. Lumbar pain when standing or bending down is related to the following factors: 1. Lumbar disc herniation: it is mainly caused by squeezing the spinal nerves at the back when bending down, which can radiate to the thighs, calves or ankles and produce pain symptoms. 2. Strain injury of lumbar muscle: pain can occur when the muscle changes its shape after standing for a long time, and the length of the muscle changes when bending. 3. Lumbar sprain: muscle strain during strenuous exercise, heavy lifting, bending can make the injured muscle pain. Lumbar standing does not hurt a bending pain may also be cold, trauma, etc., it is recommended to go to the hospital, improve the examination to clarify the cause of the disease, to give targeted treatment or treatment.