The sacrum is a bone at the back of the pelvis between the hip bones. A sacral fracture can cause symptoms including lower back and buttock pain, swelling, and reduced bowel and bladder control.

When the sacroiliac joints become inflamed or irritated, it can cause lower back pain and stiffness. This is known as sacroiliitis. In some cases, the pain may also radiate into the hips, buttocks, or ...