There are many reasons for the swelling and pain in the caudal vertebrae area, and the common ones are lumbar disc herniation, perianal abscess, sacroiliac arthritis and so on. 1. Lumbar disc herniation: due to lumbar intervertebral disc degeneration, partial or total rupture of the annulus fibrosus and nucleus pulposus, compression of the surrounding tissues can cause pain and swelling in the caudal region with a sense of falling. 2. Perianal abscess: acute purulent infection occurs in the soft tissues around the anorectal canal or the peripheral space, which can spread along the direction of lymphatic drainage and cause distension and pain in the caudal vertebrae area, and there can be a sensation of falling. 3. Sacroiliac arthritis: the supportive force of lumbosacral muscles and ligaments is weakened, and the articular cartilage is worn out, which causes osteophytes and inflammatory reaction of sacroiliac joints, and manifests as lumbago, distention and pain in the caudal vertebrae area, and a sense of falling. Coccygeal area distension with falling sensation may have other reasons, such as exertion, trauma, etc., should go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and standardize the treatment under the guidance of the doctor.