How Does the Hip Joint Work?
- The hip joint is a ball and socket joint, formed at the junction of the femoral head, or hip bone, and the acetabulum, or hip socket. The femoral head, which is the only movable part of the hip joint, is designed to glide and rotate within the socket as the hip moves.The acetabulum is immobile and remains in a fixed position. The femoral head is round and is designed to fit snugly inside the acetabulum. A thick, fibrous sheath of connective tissue called the hip joint capsule surrounds the hip joint and increases its stability. When the hip moves, the hip joint capsule helps to ensure a tight, snug fit of the femoral head inside the acetabulum.
- Movement of the hip joint is made possible by a series of powerful muscles that act upon the hip joint and provide the force necessary to move the hip joint through its full range of motion. Thick bands of fibrous tissue, otherwise known as ligaments, connect various muscles, including the piriformis and psoas muscles, to the hip joint. The greater trochanter, a large bony protuberance located on the lateral side of the hip joint, is a major muscle attachment point on the hip. When hip muscle actions exert force against the hip joint, the femoral head rotates to various degrees inside the acetabulum.
- Covering the femoral head, as well as lining the acetabulum, is a thick, smooth layer of articulating cartilage, which is a fibrous, dense, white tissue designed to increase hip joint flexibility and cushioning. As the hip joint moves, the articulating cartilage allows for smooth, almost friction-free movement of the joint and helps to disperse the load evenly throughout the hip. The articulating cartilage prevents the ends of the hip bones from rubbing against each other, a condition that would severely limit hip joint function and cause tremendous pain. The ability of the hip joint to function properly is related in large part to the health and condition of the hip joint cartilage.
