Lumbar back pain may be due to lumbar muscle strain, acute lumbar sprain, lumbar intervertebral disc herniation and so on. 1. Lumbar muscle strain: prolonged overexertion, degenerative changes in the lumbar vertebrae, and untreated soft-tissue injuries can cause lumbar pain, activity limitation, and spasms of the lumbar back muscles, which can lead to lumbar pain when leaning back. 2. Acute lumbar sprain: the flash of lumbar sprain triggers excessive pulling of lumbar muscles, fascia, ligaments and other soft tissues, resulting in muscle spasm and pain in the lumbar region, which can be manifested as pain when the waist is tilted back. 3. Lumbar disc herniation: degenerative changes in the lumbar vertebrae lead to lumbar disc herniation, which compresses the nerve roots around the spinal cord, causing lumbar pain, pain in the outer thighs and calves, pain in the back of the foot, and pain when leaning back. There may be other reasons for the pain when you lean back, so it is recommended that you go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy.