The coccyx, also known as the tailbone, is a small bone resembling a tail located at the bottom of the spine. It is composed of three to five coccygeal vertabrae or spine bones. The vertabrae may be fused together to form a single bone. In some cases, the first coccygeal vertabra is separate from the other three. The coccyx is connected to the sacrum by means of an amphiarthrodial joint.
The coccyx is a remnant of the vestigial tail; however, unlike most of the other vestigial parts of the body, the coccyx is not completely without function. The coccyx serves as an attachment site for tendons, ligaments, and muscles. It also functions as an insertion point of some of the muscles of the pelvic floor. The coccyx also functions to support and stabilize a person while he or she is in a sitting position.
The coccyx may be fractured when a person falls abruptly on his or her buttocks. A woman's coccyx may be broken during childbirth. A qualified medical professional may prescribe pain medication until the coccyx heals. In extreme cases, the coccyx may need to be surgically removed. This procedure is called a coccygectomy.