Hip bones and sacrum
The pelvis is a ring of bone. Its sides and front are the two hip bones. At the back they meet the sacrum at the sacroiliac joints, which barely move and are held by some of the strongest ligaments in the body. In front they meet at the pubic symphysis, a joint with a pad of fibrous cartilage.
The right hip bone from the outside, with the crest of the ilium above and the acetabulum below, Gray's Anatomy, 1918, figure 235Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray235.png)
Each hip bone forms from three bones, the ilium above, the ischium below and behind, and the pubis in front. They meet at a Y-shaped cartilage in the acetabulum, the socket for the femur, and fuse into one bone in the teens. You feel the crest of the ilium at the waist and sit on the ischia.
The pelvis passes the weight of the trunk to the legs. It also cradles the bladder, the end of the bowel and the reproductive organs.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapter on the pelvic girdle, gluteal region and thigh.
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