There are a number of causes for hip problems. The most common is osteoarthritis (wear and tear, generally related to age). Rheumatoid arthritis is a condition whereby the lining of the joint becomes extremely inflamed and starts to destroy the healthy articular cartilage. Some times the joint does not develop normally from birth (developmental dysplasia of the hip) and sometimes the blood supply to various parts of the femoral head is interrupted and this bone slowly dies (avascular necrosis). Severe trauma, such as an intra articular fracture or dislocation, can produce post-traumatic arthritis and fractures in the neck of the femur, which occur in people with osteoporosis, may also require hip replacement surgery. A hip replacement is also called a Hip arthroplasty (the technical term). Its aim is to alleviate pain and provide a near-normal range of movement. During the procedure the head and neck of the femur are removed and the inside few millimeters of cartilage and bone in the acetabulum are also removed and an artificial joint is inserted.
In some cases it may be best to replace both hip joints during the same operation. This tends to be in some patients who are confined to a wheelchair or who suffer from extreme stiffness or pain and think that rehabilitation after one may be made extremely difficult because of arthritis in the other hip. Recovery and rehabilitation tend to be a little bit more difficult and uncomfortable in the first few weeks after surgery, but there is the advantage of less total time off work for recovery.