Your hip is a ball-and-socket joint where the thighbone or femur (ball) meets the pelvis (socket). This joint is surrounded by cartilage, muscles, and ligaments that allow it to move smoothly. The cartilage is a smooth, shock-absorbing layer that covers the bones and allows the ball to glide easily inside the socket. The muscles around the joint support your weight and help move the joint smoothly so that you can walk without pain.
Arthritis of the joint is the most common reason for a hip replacement. Arthritis damages the cartilage which no longer serves as a cushion and exposes the underlying bone. This causes roughening of the bones and they rub together like sandpaper. The ball grinds in the socket when you move your leg, causing pain, stiffness and immobility. The affected leg may become shortened, muscles may become weaker and a limp may develop. The above image shows a normal hip joint in comparison to a degenerated hip joint.
There are numerous conditions that can cause Arthritis and often the exact cause is never known. In general, but not always, it affects people as they get older (Osteoarthritis). Other causes include:
Childhood disorders e.g., dislocated hip etc.
Growth abnormalities of the hip, such as shallow socket, may lead to premature arthritis.
Increased stress e.g., overuse, overweight, etc.
Avascular necrosis (loss of blood supply)
Connective tissue disorders
Inflammation e.g., Rheumatoid arthritis
Total Hip Replacement (THR) or Total Hip Arthroplasty is an operation to replace the worn or damaged parts of your hip joint. The surfaces of the diseased joint are removed and replaced with a mechanical, artificial joint called a prosthesis. This surgery can relieve the pain and stiffness in your hip joint.
Your new hip prosthesis has femur and pelvic parts made from metals and plastics. The cup replaces the worn hip socket of your pelvis. The ball replaces the worn end of your thigh bone (femur). The ball is attached to a stem that fits into your femur. The cup and stem are sometimes cemented in place with a special bone cement, or the metals may have a porous surface that bone will grow into and create a tight fit.
The prosthesis can last 10 to 15 years. However, over time it may become worn and loose and a replacement (revision) of the hip may be required.
The video animation below shows the stages of Total Hip Replacement (THR).