The pelvis is a ring formed by the two hip bones and the sacrum. It transfers body weight from the spine to the legs and protects the bladder, rectum and reproductive organs.
The hip bones
Each hip bone forms from three fused bones: the ilium on top, the ischium below and behind, and the pubis in front. All three meet at the acetabulum, the socket for the head of the femur.
The ring
The hip bones join the sacrum at the sacroiliac joints behind and each other at the pubic symphysis in front. Because it is a ring, a break in one place often comes with a second injury elsewhere in the ring.
Male and female pelvis
The female pelvis is usually wider and shallower, with a rounder inlet and a wider pubic arch that helps childbirth. The male pelvis is narrower and heavier.
Landmarks you can feel
The iliac crests, anterior superior iliac spines, pubic symphysis and ischial tuberosities can be felt through the skin and guide exams and procedures.
At the bedside
Pelvic fractures can tear large veins and arteries and cause life-threatening hidden bleeding. In a trauma patient with a suspected pelvic fracture, do not rock the pelvis, and apply a binder centered over the greater trochanters.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).