Sacrum. A spade-shaped bone that is formed by the fusion of 5 originally separate sacral vertebrae.

Coccyx (tail bone). Formed by the fusion of 4 originally separated coccygeal bones.

Three hip bones. These are:

• Ilium. The broad, flaring portion of the hip bone (the crest of the pelvis).

• Pubis. The lower, posterior part of the hip bone.

• Ischium. One of the bones that helps form the hip.

Pelvic fractures. A pelvic fracture is a break in 1 or more of the pelvic bones. It is the result of major force. Some pelvic fractures can heal on their own. But unstable or high energy fractures need surgery.

Most pelvic fractures are caused by direct hits or by a hit through the thighbone (femur). They often occur due to motor vehicle accidents, especially motorcycle accidents.

Osteitis pubis. This is an inflammation of the pubic symphysis, the slightly moveable joint of the front of the pelvis. It causes pain in the groin and soreness over the front of the pelvis. This condition is often due to repeated pelvis stress, such as kicking the ball in soccer. Rest often heals the condition.