Sacrum

A triangular-shaped bone located at the base of the spine, forming the posterior portion of the pelvis.

Anatomy

The sacrum is situated between the two hip bones (ilia) and connects the spine to the pelvis. It lies just below the lumbar vertebrae and above the coccyx (tailbone). The sacrum consists of five fused vertebrae (S1 to S5) in adults. These vertebrae are fused together to form a single, solid bone, giving the sacrum its characteristic shape. The sacrum has a natural curve, which helps to support the weight of the upper body and maintain balance when standing or walking.

Functions

Support: The sacrum provides structural support and shock absorption for the pelvis and helps distribute body weight to the lower limbs during activities such as walking, running, and standing.

Nerve Pathway: The sacrum is also an important part of the sacral plexus, a network of nerves that innervates the lower limbs, pelvis, and perineum. The sacral nerves exit the spinal column through the sacral foramina, providing motor and sensory function to these areas.

Protection: The sacrum protects the pelvic organs, including the bladder, reproductive organs, and part of the intestines.

Common Issues

Sacroiliac Joint Dysfunction

The sacroiliac joints connect the sacrum to the ilium (hip bones). Dysfunction can occur when these joints become inflamed or irritated causing pain in the lower back, buttocks, or hips, which may worsen with certain movements (e.g., standing up, sitting, or climbing stairs).

Sciatica

Although primarily related to the sciatic nerve, sacral issues can contribute to sciatica, where the nerve becomes compressed or irritated, causing sharp or shooting pain that radiates from the lower back down through the buttocks and along one leg, often accompanied by numbness or tingling.