The pelvic ligaments
Sacroiliac and sacral ligaments
Strong ligaments that lock the sacrum into the pelvis.
What it does
Some of the strongest ligaments in the body bind the sacrum to the two hip bones at the sacroiliac joints, with others running from the sacrum to the sit bones. They make the pelvis a nearly rigid ring that passes the weight of the upper body into the legs.
Surprising fact
During pregnancy a hormone called relaxin loosens these ligaments to help the pelvis widen for birth, which is why pelvic pain is common in late pregnancy.
Why it matters
Irritation of the sacroiliac joints can cause low back and buttock pain that is often mistaken for a disc problem.
Nearby
Read more
Sources
Drafted with AI help; awaiting a human fact-check against these sources.
Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.