The cup like structure, in which the femur fits into the hip bone is known as Acetabulum.
the acetabulum is referred to a concave shapoed surface of the pelvis, which have a cup like groove. This groove helps in the binding of the femur head to the hip or the pelvic bone.
The round head of the femur gets fits into this cup shaped structure and forms the hip joint. The acetabulum is formed by the contribution of ischium, ilium and the pubis.
