How does the acetabulum form the hip joint with the femur?

The human hip joint is a ball-and-socket joint formed by the articulation of the femur and the pelvis. The acetabulum—a cup-shaped cavity located on the pelvis where the ilium, ischium, and pubis bones unite—serves as the socket.123

The round head of the femur rests within this acetabular cavity, an arrangement that facilitates free rotation of the limb. To ensure smooth movement and reduce friction, the surfaces of both the femur and the acetabulum are protected by a layer of articular cartilage. Additionally, the joint is stabilized by the acetabular labrum, a layer of fibrocartilage that surrounds the socket. This structural configuration allows for a wide range of motion, including forward, backward, lateral, and rotational movements, which are essential for activities such as walking, running, and sitting.12