HIP JOINT - RELEVANT ANATOMY

The hip joints are the main connection, between the lower limbs and the torso. The weight of the body gets transmitted through both these joints into the leg. They are surrounded by many bulky muscles, therefore are difficult to feel and examine.

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The hip is a unique joint, because it allows movement in all directions and at the same time, it is quite stable. Movement and stability both are possible because of it's ball and socket like structure (see graphic below). Further stability is provided by strong ligaments.

At times this stability of the hip joint is compromised when the foetus is developing in the womb. This causes the ball to move out of the cup. This condition is called Congenital Dislocation of Hip

The ball is the head of the femur and the socket is the acetabulum. The acetabulum is as part of the bony pelvis. These are surrounded by the capsule (fibrous structure attaching to bone and enclosing the joint). The capsule is strengthened by three ligaments (tough fibrous band like structures attaching bone to bone).

The hip joint is lined by a smooth, tough and resilient tissue called cartilage. This tissue allows smooth movement of the joint. In Hip Osteoarthritis this tissue gets thinned down and worn out.


STRUCTURE OF THE HIP JOINT

First is the iliofemoral or Y ligament. It is the toughest ligament and is situated anteriorly (in the front ). It is taut in extension, and hence stabilizes the hip in standing position. Inferiorly ( below ) is the pubofemoral ligament. Posteriorly is the ischiofemoral ligament.

ligaments of hip joint Further deepening this joint, is a firm fibro-cartilaginous rim, attached to the margin of the acetabulum called acetabular labrum. A ligament attaches to the head of the femur called ligamentum teres. It provides a passage to blood vessels, supplying the head of the femur during growth.

hip joint ligaments

hip ligaments model

The inner aspect of the joint is lined by synovial membrane. Over the neck of the femur, the synovial membrane is folded into ridges called retinacula. These are enclosed arteries, and are the main blood supply to the head of the femur. These arteries can easily be disrupted, by a displaced Fracture Neck Femur. Many other conditions can also disrupt the blood supply of the head of femur, such as alcoholism and steroid use. This can lead to a disorder called Avascular Necrosis.

cross section of hip joint

When blood supply of the head is disrupted during childhood it results in deformation of the head. This condition is called Perthes Disease.

Many muscles act across this joint and cause different movements. Movements occurring in the hip joint are

1.Flexion: approximation of the thigh to the front of the torso.

2.Extension: movement of the limb backwards. It is very much limited by the Y ligament.

3.Adduction: movement of the limb across and over the opposite thigh.

4.Abduction: movement of the limb sideways away from the body.

5.Rotation: movement in a circle over a point.

Main muscles causing flexion are the iliopsoas. Main extensor is the gluteus maximus. Abduction is by gluteus medius and minimus. Adduction by the adductor group of muscles.

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This page was last updated on 28th May 2009


Common causes of hip pain...

Congenital Dislocation of Hip

Perthes disease

Hip Fracture

Hip Joint Osteoarthritis

Avascular Necrosis

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