The hip joint is one of the most flexible joints in the body and is also one of the largest load bearing joints in the body. The hip joint is comprised of part of the pelvic bone called the acetabulum and part of the thigh bone called the femur. The femur is the longest and heaviest bone in the entire body. The hip joint allows for a wide range of motion, enabling the leg to move and rotate while the body remains stable and balanced.
The pelvis is located in the lower torso of the body and is responsible for protecting the organs of the abdominal cavity. It also provides an anchor for the muscles of the hip, thigh and abdomen. In childhood the pelvis is made up of many smaller bones that will eventually fuse together in adulthood. The pelvis is made up of three bones: the ilium, the ischium and the pubis. The point where these three sections fuse is the location of the acetabulum, which is the socket of the hipbone – where the head of the femur is located. The articular cartilage is the smooth tissue that covers the femoral head and the acetabulum. The articular cartilage protects the bones and makes it easier to move by allowing the bones to glide over one another with little friction as the ball (femoral head) moves around in the socket (acetabulum). Articular cartilage can become damaged as a result of injury and normal wear and tear as a result of the aging process.
The acetabulum is also surrounded by tough fibrocartilage called the acetabular labrum. This cartilage increases the depth of the socket while allowing the ball to move around freely without slipping out of alignment in the socket. The acetabular labrum increases the strength of the hip joint. Injuries to the acetabular labrum can occur as a result of repetitive hip motion or from trauma to the hip.