What does the acetabulum articulate with?

The acetabulum is a fossa (joint concavity) that is formed by the intersection of the ilium, ischium, and pubic bones of the pelvis. It is a fairly deep fossa that offers a lot of stability and mobility to the hip joint. There is a labrum made of a ring of cartilage around the rim to increase the depth of the socket and congruency of the joint. The head of the femur is seated in the fossa, and a ligament and joint capsule helps to hold the hip joint together.