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U.S. Department of Health and Human Services

Medical Devices

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The Hip Joint

The hip joint is a ball-and-socket joint. The ball portion of the hip joint (femoral head) fits into the socket (acetabulum) of the hip bone (pelvis). The bone of the femoral head and acetabulum of the pelvis are separated by spongy material (cartilage) and by a sac of fluid (synovial fluid), both of which serve to lubricate the joint. A properly functioning hip joint is critical for normal everyday activities such as walking, running and climbing.

Drawing of a normal hip joint with femur bone topped by femoral head positioned against the acetabulum of the pelvis.

The cartilage or bones that make up the hip joint can deteriorate for a variety of reasons, leading to pain, stiffness or difficulty walking.

Drawing of a diseased hip joint with femur bone topped by diseased and deteriorating femoral head positioned against the acetabulum of the pelvis.

Painful hip conditions can be treated in several ways including physical therapy, exercise and medications. When a patient’s symptoms do not respond to these treatments, an orthopaedist may recommend traditional hip replacement surgery or hip resurfacing surgery.