acetabulum

The acetabulum is the cup-shaped socket of the hip joint, formed by the fusion of the ilium, ischium, and pubis in the os coxae. It faces laterally and somewhat anteriorly and receives the head of the femur to form the ball-and-socket hip joint. The rim is deepened by the acetabular labrum, a fibrocartilaginous ring that enhances depth and stability. The non-articular acetabular fossa lies at its center and contains fat and the attachment of the ligamentum teres femoris, which extends to the fovea capitis of the femoral head. The inferior border features the acetabular notch, which is bridged by the transverse acetabular ligament to form a foramen for vessels and nerves supplying the joint surface.

Articular surface and structure: The lunate surface constitutes the majority of the articular hyaline cartilage that bears weight and allows smooth movement of the femoral head. The labrum augments joint stability by increasing the depth of the socket and enhancing seal to retain synovial fluid.

Vascular and neural supply: The acetabulum and hip joint receive arterial supply from the superior and inferior gluteal arteries and branches of the obturator artery. Innervation for the joint is provided by articular branches from the femoral, obturator, and sciatic nerves.

Clinical relevance: Variations in acetabular depth and version can affect hip stability and predispose to dysplasia or impingement. Acetabular fractures or dysplasia may contribute to early osteoarthritis and functional impairment.