The hip joint is designed for both mobility and stability. It is made up of the articulation between two bones: the pelvis and the femur (the thighbone). This is a large ball-and-socket joint. The ball is the rounded end (head) of the femur that fits in the socket which is a rounded depression in the side of the pelvis (acetabulum). This anatomy provides good stability and allows for a lot of motion within the joint e.g. walking, running, and climbing.
The femoral head is attached to the rest of the femur by a short segment of bone called the femoral neck. At the top of the femur, next to the femoral neck, there is another bump on the outside of the hip called the greater trochanter to which muscles attach.
Cartilage covers the ends of the bones and helps prevent friction between the femoral head and the acetabulum. It is slippery to allow the joint surfaces to slide against one another without causing any damage. The function of articular cartilage is to absorb shock and provide an extremely smooth surface to make motion easier
Surrounding the hip joint are many tough ligaments that prevent the dislocation of the joint. The strong muscles of the hip region moves the hip joint in all directions and help to hold the hip joint together and prevent dislocation.
Where friction occurs between muscles, tendons, and bones there is usually a structure called a bursa. A bursa is a normal thin sac of tissue that contains fluid to lubricate the area and reduce friction. Inflammation of any bursa may be a source of pain.