One of the most important joints in the human body and allowing us to walk, run, and jump, the hip is "ball-and-socket" joint. The socket is formed by the acetabulum, part of the large pelvis bone and the ball is formed by the femoral head.Functionally, the hip joint enjoys a very high range of motion, the ball-and-socket structure of the joint allows the femur to circumduct freely through a 360-degree circle. Surrounding the hip joint are many tough ligaments that prevent the dislocation of the joint. If a knee or hip joint breaks in an accident or wears out in old age, a surgeon can replace it with a ball-and-socket joint made from metal and plastic and engineered in such a way that it will duplicate the motions of a human joint. The strong muscles of the hip region also help in holding the hip joint together and preventing dislocation. The surfaces of the ball and socket are covered with articular cartilage, a smooth, slippery substance that protects and cushions the bones and enables them to move easily.
