Image credit: Memorial University of Newfoundland.
The acetabulum is the point where the three components of the pelvis (ilium, ischium, and pubis) meet. The upper part and sides of the acetabulum form the horseshoe-shaped articular surface known as the lunate surface (clearly visible in the illustration). The inferior margin is deficient and is marked by the acetabular notch. The floor of the acetabulum is nonarticular and is called the acetabular fossa.