Back pain when backward bending, but not forward bending, may be due to the following causes: 1, may be the existence of posterior side of the spinal canal of the occupying lesions caused by, for example, in the posterior side of the spinal canal there is hypertrophy of the ligamentum flavum, calcification, or the existence of serious osteophytes here, in the patient backward bending, it is possible that the nerve roots in this compression, stimulation, and thus cause back pain. The process of bending forward will keep the nerve roots away from these stimuli and make the pain symptoms disappear. 2. There may be lumbar muscle spasm. If there is lumbar muscle spasm, the patient in the process of bending backwards, may make the muscle tension in the lumbar area intensify, which in turn makes the pain appear. In contrast, when the patient bends forward, the muscles of the lumbar region will relax briefly, and the pain will be greatly relieved at this time. 3. There may be avulsion fractures in the front of the vertebral body. It is relatively rare in the clinic, often due to the patient’s excessive, sudden backward bending, resulting in avulsion fracture of the ligament attachment point in front of the vertebral body, which will appear to hurt when bending backward and reduce pain when bending forward.