About Knee Replacement Surgery
Overview of the Procedure
(Figure 1) The knee joint is a hinge joint that bends (flexion) and straightens (extension). It is formed by three bones; the lower end of the femur (thigh bone), the upper end of the tibia (shin bone) and the patella (knee cap).
Ligaments (bands of tissue) connect the bones and guide the motion. In a healthy knee joint the ends of the bones are covered with articular cartilage, which allows smooth pain free motion. A common reason for knee replacement surgery is related to the wearing away of cartilage leading to pain and limited mobility.
As a patient considering total knee replacement surgery (TKR), you probably have many questions. This information will help prepare you for what to expect during your hospitalization and rehabilitation.
Total knee replacement surgery is done to replace an arthritic or badly damaged knee joint with man-made parts. The man-made part is called a prosthesis (prohs-thee-sis) and is made of a combination of materials including metal and polyethylene (or plastic). Your surgeon will choose the prosthesis that is best for you. The goal of TKR surgery is to increase mobility and lessen pain. Total knee replacements are also called total knee arthroplasty (TKA).
During knee replacement surgery, the surgeon makes an incision over the affected knee to expose the knee joint (shown in Figure 2). The surgeon then moves aside the patella (kneecap) to reach the joint surfaces.
The surgeon shapes the lower end of the femur and the upper end of the tibia, in preparation for the prosthetic implants. The implants are designed to completely replace the surfaces of the knee joint (shown in Figure 3). If cement is used, it is placed on the ends of the femur and the tibia. The implants are inserted into the ends of those bones. A plastic “button” may be attached to the undersurface of the kneecap to replace the arthritic surface. In some cases, replacement of the kneecap is not necessary. A drain tube may be placed into the wound, and the wound is closed. A bandage is applied.
Unicompartmental Knee Replacement
Another procedure to repair knees is called a unicompartmental knee replacement (shown in Figure 4). This procedure is done when damage to the knee is limited to one side of the joint, a condition called single compartment degenerative disease. In this procedure, the worn portion of the knee joint is resurfaced while the remainder of the knee joint is left unchanged.
The procedure is done through a shorter incision than a regular knee replacement. The materials used are the same, but the prostheses are smaller than the ones used for regular knee replacement. The operative time is about the same. Your activity progression may be quicker.