The structure indicated is the acetabulum of the pelvis.
The acetabulum is formed from the point joining the three bones of the pelvis (ilium, ischium and pubis), and is the site of articulation with the head of the femur. The femoroacetabular articulation is known as the hip joint.
The acetabulum consists of two parts:
- Articular part
- Non-articular part
The non-articular part consists of the acetabular fossa and the acetabular notch inferiorly. The ligamentum teres attaches at one end to the acetabular notch, and at the other end to the fovea capitis of the femur. The articular part forms a rim surrounding the acetabular fossa, serving as a point of attachment for the acetabular labrum. This labrum is a ring of cartilage which functions to deepen the cavity of the acetabulum, stabilising the hip joint and making it structurally more difficult for the head of the femur to dislodge from its acetabular articulation.