Chronic low back pain may be caused by trauma, osteoporosis and ankylosing spondylitis. 1. Trauma: For example, fracture or dislocation of the lumbar vertebrae or some more serious sprains of the psoas major muscle. After recovery, there may be some pain left in the area, which may be aggravated by rain or exertion on cloudy days. 2. Osteoporosis: Osteoporosis can also cause low back pain, which mainly occurs in the elderly. In addition to low back pain, other joints may also experience pain, which can be diagnosed by measuring bone density. 3. Ankylosing spondylitis: Ankylosing spondylitis is a rheumatic autoimmune disease, which is mainly characterized by spinal hyperplasia and sclerosis. In addition to pain, spinal movement is also greatly restricted. When patients have long-term back pain that is difficult to relieve, it is recommended to go to the hospital in time for examination, and then targeted treatment after a clear diagnosis.