The cause of tailbone pain may be the following: 1. It may be ankylosing spondylitis, which is often preceded by tailbone pain and then gradually moves upward, mainly manifesting as HLA-B27 positivity, a rheumatic disease. 2. Tailbone pain may be caused by fasciitis or strain. 3. Spinal tumors or tuberculosis can also cause tailbone pain. 4. The pain may be caused by a herniated disc, which compresses the nerve and causes radiating pain in the tailbone.5. It is clear whether the pain is caused by other diseases, such as gouty arthritis, rheumatoid arthritis and other rheumatic diseases.