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Oxford University Hospitals NHS Foundation Trust
Hip and Knee

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About the Hip

Diagram of the hip joint

The hip joint is a ball and socket joint. The ball is the head of the femur and the socket is the acetabulum which is formed from the three bones that make the pelvis.

Covering the end of the femoral head and lining the acetabulum is a layer of articular cartilage. The articular cartilage cushions the ends of the bones and allows easy movement of the joint.

Around the edge of the acetabulum is a thickened piece of fibro cartilage which effectively deepens the socket, called the labrum. There is a strong joint capsule reinforced by several ligaments.

Lining the capsule is the synovial membrane which produces the lubrication fluid for the hip joint. The synovium is what gets inflamed in rheumatoid arthritis.

Around the joint are the surrounding muscles. These make the hip a very stable joint usually.