Sitting and bending with back pain may be caused by lumbar vertebral small joint disorder, lumbar ligament injury, acute attack of lumbar disc herniation and so on. 1. Disorders of the small joints of the lumbar vertebrae: the misalignment of the small joints of the lumbar vertebrae will cause the synovial membrane to easily enter the joint space, resulting in incarceration, which will cause lumbar pain, especially when bending over, there will be more serious pain. 2. Lumbar ligament injury: If there is lumbar ligament strain, low back pain is caused by the lumbar ligaments will be stretched excessively when doing bending exercise, which will lead to low back pain. 3. Acute attack of lumbar disc herniation: Lumbar disc herniation compresses the dural sac, which can cause lumbar pain, as well as functional limitations and pain. Sitting and bending back pain may also be seen in lumbar muscle strain, osteoporosis and other diseases, if the symptoms of sitting and bending back pain, persistent unrelieved, need to seek medical treatment.