Hip (anatomy)

From ArticleWorld

The hip is a broad term that can refer to the actual hip joint, which connects the pelvic bone to the femur or to the area that projects outward from the femur, the greater trochanter, to form the point that one feels when touching the hip area.

Anatomy

The hip joint is a true ball-in-socket joint, where the ball is the proximal end of the femur and the socket is formed by a single aspect of the pelvis called the acetabulum. The joint surfaces are smooth and covered by a lubricated joint cartilage. There is a rim around the acetabulum that is made of a fibrous ring of cartilage that forms a vice-like grip all around the head of the femur, keeping it in place.

The hip is supported by a strong joint capsule that encases the joint and by three supportive ligaments. The iliofemoral ligament supports the front of the joint. It is considered to be one of the strongest ligaments of the body and prevents excessive extension of the hip. The pubofemoral ligament attaches the pubic rim of the pelvic bone to the femur. It supports the underside of the joint. Behind the joint are the ischiofemoral ligament and a smaller ligament, known as the ligamentum teres, which supplies a tunnel for the arterial supply to the head of the femur.

Several important nerves and blood vessels pass in front of the hip joint after exiting the body via the pelvis. The femoral artery can be felt in the groin area. The sciatic nerve passes near the area as well as the external iliac vein.

Function

The hip has a very wide range of motion. It can flex forward and extend backward. It can abduct, or draw away from the body, and can adduct, or draw the leg toward the body. It can also internally rotate, which means to rotate toward the front of the body. It can similarly externally rotate, which allows it to rotate away from the body.

The hip has powerful muscles. The iliopsoas muscle flexes the hip joint. This is a muscle with two parts: the psoas muscle originating higher inside the abdomen and the iliacus muscle that originates in the pelvis itself. The hip extensor muscles are the gluteus maximus muscle and the hamstring muscles. Smaller muscles around the joint allow for abduction, adduction and rotation of the hip.

Conditions

The pelvis can fall victim to several conditions. A fall in the elderly can cause the hip to fracture, generally somewhere above the greater trochanter. More rarely the hip can dislocate in someone who doesn’t have a very deep acetabulum so that the ball joint slips out during trauma. The other condition that can affect the hip is called necrosis of the head of the femur. Because the femur is supplied by only a single small artery, the arterial supply can be disrupted or insufficient so that the head of the femur can die off. This condition can occur due to trauma or in childhood, as a congenitally-poor blood supply to this part of the bone.