The pelvic skeleton is composed of two hip bones, sacrum, and coccyx.

• Hip bones (2) - each is composed from three bones:
  • Ilium
  • Ischium
  • Pubis

The three bones fuse together during puberty and ossify around age 25. The left and right hip bones join in the pubic symphysis.

• Sacrum - a triangular-shaped bone at the base of the spine, which is formed by 5 sacral vertebrae that are fused with each other (it happens between ages 18 to 30).
• Coccyx - also known as the tailbone, the final bony segment of the spine, which consists of 3 to 4 rudimentary vertebrae fused together.