Sudden cramp-like pain in the lower back may be caused by acute injury, lumbar muscle strain, lumbar intervertebral disc herniation, etc., and you should consult a doctor in time to find out the cause. 1. Acute injury: Acute injury to the lumbar region causes tears in the ligaments, fascia and muscles, which may lead to sudden cramp-like pain in the lower back. 2. Lumbar muscle strain: If the lumbar muscles are chronically strained for a long period of time, it may lead to lumbar muscle strain, which may cause contraction and twitching of the lumbar muscles during exercise or labor, resulting in sudden cramp-like pain in the lower back. 3. Lumbar disc herniation: it may be due to excessive weight bearing or improper activities, resulting in the protruding nucleus pulposus falling into the spinal canal, leading to the cauda equina and the nerve root acute compression symptoms, appearing as a sudden cramp like pain in the waist. There may be other reasons for the sudden cramping pain in the lower back, so you should consult a doctor in time to find out the specific cause and get appropriate treatment if necessary.