What bones make up the innominate bones?

The innominate bone is a large, complex bone that forms the pelvis. It is composed of three bones that fuse together during development: the ilium, the ischium, and the pubis.

* The ilium is the largest and uppermost of the three bones. It forms the upper part of the pelvis and flares out to form the hip bone. The ilium has a large, concave surface called the iliac fossa.

* The ischium is the lower and backmost of the three bones. It forms the lower part of the pelvis and sits below the ilium. The ischium has a large, curved surface called the ischial tuberosity, which is where you sit down.

* The pubis is the smallest and frontmost of the three bones. It forms the front of the pelvis and meets the other pubis bone in the midline of the body. The pubis has a large, triangular opening called the obturator foramen.

The innominate bones come together to form the acetabulum, the cup-shaped socket that holds the head of the femur (thigh bone). The innominate bones also provide attachment points for muscles, ligaments, and tendons that support the pelvis and allow for movement.