A joint is the point at which two bones are connected. Many joints provide support and stability and allow movement, while others, such as those of the pelvis, are not movable. Joints contain bones, cartilage, and a lining called synovium, which produces a lubricating fluid. Most joints are held together by muscles, tendons, and ligaments and are often cushioned by fluid-filled sacs called bursae. There are several types of joints, including: Hinge joints, such as the elbows and knees; Ball-and-socket joints, such as the hips and shoulders; Pivot joints, which allow rotation, such as joints in the neck allow the head to turn from side to side; and Condyloid joints, such as the wrist, which allow movement in many different directions.

Joint replacement involves surgery to replace the ends of bones in a damaged joint. This surgery creates new joint surfaces. In knee replacement surgery, the ends of the damaged thigh and lower leg (shin) bones and usually the kneecap are capped with artificial surfaces lined with metal and plastic. Usually, doctors replace the entire surface at the ends of the thigh and lower leg bones. However, it is increasingly popular to replace just the inner knee surfaces or the outer knee surfaces, depending on the location of damage. This is called unicompartmental replacement. People who are good candidates for unicompartmental surgery have better results with this procedure than with total joint replacement.1 Doctors usually secure knee joint components to the bones with cement.

In knee replacement surgery, for example, doctors remove the damaged cartilage and replace it with new joint surfaces in a step-by-step process. Often it is possible to use regional anesthesia for joint replacement surgery. That means you can't feel the area of the surgery and you are sleepy, but you are awake. The choice of anesthesia depends on your doctor, on your overall health, and, to some degree, on what you prefer. Your doctor may recommend that you take antibiotics before and after the surgery to reduce the risk of infection. If you need any major dental work, your doctor may recommend that you have it done before the surgery. Infections can spread from other parts of the body, such as the mouth, to the artificial joint and cause a serious problem.