The hip is a ball-and-socket joint formed by the pelvis and the femur, or thighbone. The ball is the top end of the thighbone and the socket is a cup shaped area on the outside of the pelvis.
Both surfaces of contact are lined with smooth cartilage that keeps the hard bones from rubbing directly on one another. This allows for smooth, low-friction motion.
The hip joint is held together by several structures. The first is the joint capsule that surrounds the joint. This capsule is tissue that attaches to each side of the joint and helps keep lubricating fluid inside the joint. There are also strong ligaments or bands of fibers outside the joint that provide stability and help prevent dislocation of the hip. Lastly, numerous muscles provide a wide range of motion and also help keep the hip stable.
The hip can be subjected to force that is three to nine times your body weight, depending on the activity.