OSTEOARTHRITIS – The leading cause of joint replacement
The knee joint can develop arthritis over time, leading to a complete wear of the articular cartilage. When this point has been reached in the development of the disease, a partial or a total knee replacement is usually necessary to relieve pain and restore function by replacing the worn cartilage with an artificial bearing on both the lower extremity of the femur (the thigh bone) and the top of the tibia (the main lower leg bone).
TOTAL KNEE REPLACEMENT
Total Knee Replacement employs specially designed components, or prostheses, made of metals and/or plastics, to replace the cartilage in your knee. The metal that is most commonly used is an alloy of cobalt, chromium and molybdenum. The plastic is ultra-high molecular weight polyethylene. These materials have been used in joint replacement for about 30 years and their behavior in the body is well-known.
In modern total knee replacement surgery, only the worn-out cartilage surfaces of the joint are replaced. The entire knee is not actually replaced. The operation is basically a “re-surfacing” (or “re-tread”) procedure. Only a small amount of bone is removed, the collateral ligaments are left intact, and the muscles and tendons are left intact. Alignment abnormalities can usually be corrected during the operation by adjusting the direction of the cuts of the bones, removing bone spurs (osteophytes), and lengthening tight ligaments. Front and side views of a knee following total knee replacement are shown below. Note that the smooth surfaces of the joint are restored. The joint space is now comprised of polyethylene. The operation only replaces the worn surfaces of the joint. The ligaments, tendons and muscles are retained.