Once you are under general anesthesia (meaning you are temporarily put to sleep) or spinal/epidural anesthesia (numb below the waist), an 8- to 12-inch cut is made in the front of the knee. The damaged part of the joint is removed from the surface of the bones, and the surfaces are then shaped to hold a metal or plastic artificial joint. The artificial joint is attached to the thigh bone, shin and knee cap either with cement or a special material. When fit together, the attached artificial parts form the joint, relying on the surrounding muscles and ligaments for support and function.