Total Knee Replacement
What is a total knee replacement (arthroplasty)?
Patients often ask, "What exactly is a total knee replacement?" The simplest answer is that it is a replacement of the worn and arthritic surfaces for the knee joint. A knee replacement is similar to resurfacing a road full of potholes. A total knee replacement puts an artificial surface on all parts of the joint that contact each other as the knee bends.
With arthritis, the cartilage covering the ends of the bone within the knee joint is badly worn. In a knee replacement, this damaged cartilage, along with a very small amount of bone, is removed with precise guides and instruments. The knee replacement implant, which is made of metal and plastic in a variety of sizes, is then fitted to the bone to provide an artificial surface that causes no pain.
What is a partial knee replacement?
Partial knee replacement (usually called a unicompartmental replacement) is done if only part of the knee joint is damaged by arthritis. Think of the knee as having three compartments: an inside, outside, and a front compartment for the kneecap. Most frequently, it is the inside compartment that becomes arthritic. The decision to perform a partial replacement is made only if other compartments have healthy, normal cartilage at surgery.
A Brief History of Knee Replacements
Knee replacement surgery was first performed in the 1960's with hinged type of implants that did not work well. The problem was early loosening because a hinge did not permit the natural rotation and bending of the knee. These early implants also had high infection rates.
In the mid seventies better implants, called condylar total knee implants, were designed. They came in only two sizes and were solid pieces. Othopaedists were cautious about using them because of their experience with hinges, but as good results were recognized, more surgeons performed the operations. Implant companies then designed implants that were easier to place, as well as better instruments that made the surgery more reproducible. By the nineties, knee replacement surgery was widely accepted as a good operation with excellent pain relief from arthritis. So the change that made the most difference was an implant that let the knee rotate and allowed the ligaments to provide stability.
Future changes for relief of knee pain
Better instruments and new techniques have permitted us to put implants in more easily and through smaller incisions. By cutting less muscle and utilizing more aggressive techniques of pain control, patients are recovering faster. New materials and designs are constantly becoming available, giving the potential for implants with improved longevity.
Changes in the next century will likely be aimed at developing medicines and procedures to delay or prevent the development of arthritis. Furthermore, the orthopaedic community anticipates that biologic devices may be developed for repairing damaged joints, rather than inserting mechanical devices. These areas of research are currently being heavily investigated, however, it will still be years until proven techniques become available that approach the success of total joint replacement.
Knee education booklet
The physicians at the Anderson Clinic emphasize patient education prior to surgery, and have developed a patient education booklet. To view a PDF file of this booklet, click here.
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Physicians with special interest in Total Hip and Knee Replacement