An Introduction to Knee Replacement Surgery

When it seems like you've tried everything and still don't have any relief from your knee pain and debilitation, it may be time to consider knee replacement surgery. There are two different types of knee replacement procedures your doctor may recommend to relieve your knee pain, partial knee replacement, also called uni-compartmental replacement, or total knee replacement. Learning the differences can help you have a better discussion with your doctor.

In knee replacement surgery, the ends of the bones that make up the knee are repaired. The new joint works the way cartilage works in a healthy knee by preventing the bones of the leg from rubbing together at the joint.

The Knee Joint

The knee is the largest joint in the body. It is commonly referred to as a “hinge” joint because it allows the knee to flex (bend) and extend. While hinges can only bend and straighten, the knee has the additional ability to rotate (turn) and translate (glide). The knee joint is formed by the tibia (shin bone), the femur (thigh bone) and the patella (knee cap). Each bone end is covered with a layer of smooth, shiny cartilage that cushions and protects while allowing near frictionless movement. Cartilage, which contains no nerve endings or blood supply, receives nutrients from the fluid contained within the joint.

Total Knee Replacement

Total knee replacement, or arthroplasty, is the relining of the joint (bone end surfaces) with artificial parts called prostheses. There are three components used in the artificial knee. The femoral (thigh) component is made of metal and covers the end of the thigh bone.

The tibial (shin bone) component, made of metal and polyethylene (medical-grade plastic), covers the top end of the tibia. The metal forms the base of this component, while the polyethylene is attached to the top of the metal to serve as a cushion and smooth gliding surface.

The third component, the patella (kneecap) may be all polyethylene or a combination of metal and polyethylene.

The new components are stabilized by your ligaments and muscles, just as your natural knee.

In some cases, total knee replacement can be done through a smaller incision. This is called minimally invasive total knee replacement.

Partial Knee Replacement

If X-ray and MRI (Magnetic Resonance Imaging) results tell your surgeon only one side of your knee is damaged, your surgeon may decide a partial knee replacement is right for you. Partial knee replacement repairs the side of the knee joint that is damage instead of the entire joint surface as in total knee replacement.

Because only one side of the knee is being replaced, a small incision may be used. Because of the small incision, this is sometimes referred to as “minimally invasive” surgery.

Partial knee replacement is not usually considered for active or heavy people because they can put too much stress on the implant. In addition, if two or more compartments of your knee are damaged, your surgeon will probably recommend total knee replacement.

The way a knee replacement will perform depends on your age, weight, activity level and other factors. There are potential risks and recovery takes time. If you have conditions that limit rehabilitation, you should not have this surgery. Only your orthopaedic surgeon can decide whether partial or total knee replacement is right for you.

Last Updated: 12/12/2006