The sacrum is a shield-shaped bony structure that is located at the base of the lumbar vertebrae and is connected to the pelvis. The sacrum forms the rear wall of the pelvis and strengthens and stabilizes the pelvis. Joined to the very end of the sacrum are two to four tiny, partially fused vertebrae, known as the coccyx or "tail bone." The coccyx provides slight support for the pelvic organs but is actually of little use.
Review Date: 1/25/2013
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.