This 3D animation by The Human Atlas explains Knee Replacement.

The skeletal system is made up of more than 200 bones that support the body's weight and protect the internal organs. The knee joint supports a large amount of weight and, over time, can suffer structural damage.

The knee comprises three main bones: the patella, or knee cap; the femur, or thigh bone; and the tibia, or shin bone. When the cartilage that covers the surfaces of these bones wears down, simple movements can become painful and cause swelling.

Normal aging or knee injury can cause symptoms requiring knee replacement surgery. During knee replacement surgery, the lower part of the femur and upper part of the tibia are removed and replaced with metal and synthetic pieces that are identical to the injured joint and bone. In some cases, the back side of the patella is also removed.

The purpose of knee replacement surgery is to reduce localized pain and swelling. The synthetic joint allows greater freedom and mobility.

There are several potential complications associated with this procedure that should be discussed with a doctor prior to surgery.