Sudden pain in the lower back may be caused by lumbar muscle strain, lumbar intervertebral disc herniation, and nerve root edema in the acute stage. 1. Lumbar muscle strain: due to overwork or incorrect posture, the lumbar back muscles are in a state of high tension for a long time, resulting in excessive muscle tension and local reactive inflammation, which causes pain in the lumbar back without any obvious trauma, and in addition to the pain, nodules can also appear. 2. Lumbar disc herniation: Lumbar disc herniation is a disease in which the nucleus pulposus protrudes and compresses the nerve root after the rupture of the annulus fibrosus of the intervertebral disc, causing lumbar and leg pain as the main manifestation. It can be caused by degenerative lesions of lumbar intervertebral discs and external forces. The pain in the lower back is often accompanied by pain in the lower limbs, such as radiating pain in the buttocks, the back of the thighs, the outside of the calves to the roots or the back of the feet. 3. Acute neurogenic edema: it is a kind of neuroinflammatory disease caused by degeneration of bones, injury to nerves or allergy to food and drugs, etc. Localized nerve pain or numbness may occur. Localized nerve pain or numbness may occur. Other diseases or infections may also cause sudden pain in the lower back, and you need to go to the hospital in time and have a checkup before you can identify the cause and treat it.