Approximately 1% to 5% of adults develop fractures due to bone weakness, which are known as insufficiency fractures. In some patients, these fractures arise in the sacrum, the bone at the back of the pelvis that is connected to the spine. A sacral insufficiency fracture is a type of stress fracture that often occurs due to normal stress on bone that has been weakened by osteoporosis. Other potential causes of sacral insufficiency fractures include steroid therapy, rheumatoid arthritis, and radiation treatment of the pelvis or a nearby tissue. These fractures occur primarily in women and common symptoms are groin, lower back, and/or buttocks pain that is usually severe enough to prevent or limit walking. For most patients, insufficiency fractures improve substantially or resolve during conservative nonsurgical treatment.