The pain in the posterior lumbar region is suddenly like a cramp: 1, it may be a patient with a herniated lumbar disc, due to heavy lifting or improper activity, causing the herniated nucleus pulposus to fall into the spinal canal, resulting in acute compression symptoms on the cauda equina and nerve roots, which can cause cramp-like pain. 2, it may also be due to the presence of osteoporosis in the elderly, a sudden compression fracture of the lumbar region, resulting in acute cramp-like symptoms. It should be fixed by braking, and related examination and bed rest.3. It may also be due to acute injury to the lumbar region causing tearing of muscles, fascia and ligaments, resulting in acute cramp-like pain. If this is the case, you can play a good protective treatment role by braking the lumbar circumference, then bed rest and local physiotherapy. If there is no relief within a short period of time, you must go to a regular hospital in time.