Sudden pain and immobility in the lower back may be due to acute lumbar sprain, lumbar disc herniation, kidney stone, lumbar spine fracture and other diseases. 1. Acute lumbar sprain: patients may cause lumbar sprain when lifting heavy objects or carrying out strenuous activities. Acute lumbar sprain usually manifests itself clinically as restricted movement and lumbar pain. When the situation is serious, it may cause muscle spasm, localized pressure and pain, as well as deformity of the lumbar region. 2. Lumbar disc herniation: acute attack of lumbar disc herniation can also cause sudden pain in the lower back and inability to move. In serious cases, patients may experience radiating pain in the lower limbs and numbness in the lower limbs, and some patients may even have defecation problems. 3. Kidney or ureteral stones: kidney stones or ureteral stones in the acute stage may also occur suddenly severe pain in the lower back, limited mobility. 4. Lumbar spine fracture: when there is a fracture of the lumbar spine or transverse process, sudden pain in the lower back and immobilization may occur because of pain. Sudden pain and immobility in the lower back may also be due to lumbar bone tumor, lumbar myofasciitis and lumbar back vascular embolism, etc. Patients should be treated in time.