Each hip bone consists of three bones: 

• Ilium

• Ischium

• Pubis

Several structures on each side form between the three bones composing the hip bone, such as the acetabulum and obturator foramen.

The obturator foramen is a large opening on each side of the pelvic skeleton formed by the ischium and pubic bones. The obturator artery, vein and nerve pass out of the pelvis through this foramen.