Total Knee Replacement
When the arthritis in the knee has progressed to the stage that the articular cartilage is all worn away, then the arthritis is advanced enough that only knee replacement surgery can relieve the pain and improve the function for the patient. Arthritis is simply a loss of the articular cartilage, and this is a mechanical problem and not a biological disease for most patients who have the typical form of arthritis, named osteoarthritis. Patients who have rheumatoid arthritis and other inflammatory disease, do have a more biological form of arthritis. The early stages of arthritis, whether mechanical or biological, may be treated through a combination of medication, physical therapy, and injections. However, once the cartilage has been lost so that the bones are rubbing together, there is little relief of pain except by knee replacement, which is the operation that implants new surfaces on the articular ends of the bone.
Many people have the impression that knee replacement surgery is like an amputation of the knee, and that the knee is cut away by removing the lower end of the femur and the upper end of the tibia, and that some form of metal hinge is placed between these two bones. This is the wrong image of knee replacement surgery. The image you should have in your mind is that this operation is one that simply substitutes for the lost articular cartilage. Because we do not know how to make cartilage, we have to use different materials to replace the lost cartilage. The materials that we use are metal against plastic. Only enough bone is removed from the end of the femur and top of the tibia and the undersurface of the patella to replace these surfaces with a new metal against plastic articulation surface. The technique of this will be described next, so that you can better understand this. The name, total knee replacement, was given to the operation because the surface of the knee is totally replaced. (There are operations that replace only a portion of the surface, and these are described under unicompartmental replacement in the next section). The surfaces of the knee are sized to the bone of each patient's knee. There are multiple sizes because there are multiple sizes of people. Next will be described, with animation, the technique of total knee replacement.