To understand TKR, you should be familiar with the structure of the knee, a complex joint consisting of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). When you bend or straighten your knee, the end of the femur rolls against the end of the tibia, and the patella glides in front of the femur.
With a healthy knee, smooth, weight-bearing surfaces allow for painless movement. Muscles and ligaments provide side-to-side stability.
A membrane lines the joint. Cartilage acts as a cushion between the femur and tibia and is lubricated by synovial fluid.
With an arthritic knee, the cartilage cushion wears out. The bones rub together and become rough. The resulting inflammation and pain cause reduced motion and difficulty in walking.
The weight-bearing surfaces of a total knee replacement are smooth, as in a normal knee. A femoral component covers the end of the thigh bone, a tibial component covers the top of the shin bone, and the patellar component covers the underside of the kneecap.
Most femoral components are metal alloys (cobalt chromium) or metal ceramic alloys (oxidized zirconium). The patellar component is plastic (polyethylene); the tibial insert component is also plastic (polyethylene); and the tibial tray component can be made of the following materials:
Clinical and biomechanical research has steadily refined knee replacement methods and materials. Prosthesis durability can vary from patient to patient because each patient’s body places slightly different stresses on the new knee. However, the average patient can expect to obtain greater mobility and freedom from pain, which will, in turn, improve ability to walk.