The hip joint is one of the body’s largest joints and is a ball and socket joint. The ball is the upper end of the thigh bone and the socket is the cup of the hip bone or pelvis. The bone surfaces of the ball and socket are covered with articular cartilage, a smooth tissue that cushions the ends of the bones and enables them to move easily. A thin tissue called the synovial membrane surrounds the hip joint and this makes a small amount of fluid that keeps the joint lubricated and helps prevent friction on movement. Bands of tissue called ligaments connects the ball to the socket and provides stability to the joint.