The hip joint is formed by the articulation of the rounded head of the femur and the cup-like acetabulum of the pelvis. It forms the primary connection between the bones of the lower limb and the axial skeleton of the trunk and pelvis.
The surface of the femoral head and the acetabulum, where the bones come into contact, is coated with a smooth tissue called articular cartilage. The cartilage, together with a substance called synovial fluid, prevents the bones from rubbing against each other and from becoming damaged.
The main cause of hip joint diseases is the wear of the articular cartilage: osteoarthritis. This wear is perceived as pain, initially only when a load is bearing on the joint, then more and more frequently, and finally also at rest.
The increase in intensity of the pain is a slow process, sometimes over many years, and can lead to a stiff hip joint. Hip replacement is a common treatment for severe osteoarthritis. Successful hip replacement brings dramatic pain relief and improvement in the function of the hip joint.