The acetabulum is a cup-shaped socket located in the pelvis that forms the hip joint. It is where the femur, or thigh bone, fits in to create a ball-and-socket joint, allowing for a wide range of motion in the leg. The acetabulum is made up of three bones: the ilium, ischium, and pubis, which fuse together during development. This structure is crucial for weight-bearing and mobility, as it supports the body's weight during activities like walking, running, and jumping. The acetabulum is also lined with cartilage, which helps reduce friction and absorb shock during movement, contributing to the overall stability of the hip joint.