Acetabulum

Acetabulum, located on the lateral surface of the hip bone, is a deep, cup-shaped hemispherical socket. Its orientation is lateral, downward, and forward. It plays a crucial role as is it articulates with the femur’s head to form the hip joint.

Within the acetabulum, we can observe two distinct regions: 1) acetabular fossa, and 2) lunate surface. The acetabular fossa is a central, rough area without any articular surface. It is covered over by a layer of fat and lined with a synovial membrane. Surrounding the acetabular fossa is the lunate surface, which has a horseshoe-shape. The surface is covered with hyaline cartilage and contributes to the hip joint by articulating with the femur’s head.

The inferior part of the acetabulum lacks proper margins, creating a notch known as the acetabular notch. However, the gap is filled by the transverse acetabular ligament, a ligamentous structure. Along the boundary of the acetabulum, there is a fibrocartilaginous rim called the acetabular labrum, which elevates the margins. The labrum deepens the acetabular cavity, providing stability to the hip joint and limiting its range of motion.