Total Knee Replacement
What is Total Knee Replacement?
Total knee replacement is a surgical procedure that has provided dramatic pain relief to millions of people around the world. Over a million are performed each year in the United States. Total Knee Replacement is a term that has been used for decades in the field of orthopedic surgery. A more appropriate term would have been Total Knee Resurfacing, since that is what we accomplish technically during the surgery. The knee joint is a complex hinge joint that allows some rotation throughout the arc of motion. Three bones articulate together to form the knee joint: The main joint is the articulation between the end of the femur (thigh bone), and the top of the tibia (shin bone). The patella (kneecap) is a smaller, triangular-shaped bone that articulates in a groove on the front of the femur. Normally, each of these bones has a shiny, white, low friction surface of cartilage that provides pain-free function of the joint. When the cartilage surface is damaged or worn out most people will experience pain during activities, and sometimes even at rest if the disease has progressed far enough.
When is a Total Knee Replacement is Necessary?
When nonsurgical methods no longer control the pain, and knee joint has evidence of advanced cartilage wear on the x-ray, a Total Knee Replacement may be indicated. It is important for your surgeon to determine that the pain is definitely arising from loss of cartilage. There are many other conditions that cause knee pain such as meniscus tears, ligament tears, and inflammation of the tendons or bursa around the knee that are not appropriate for a knee replacement. It is also possible for disease in the hip joint to refer pain to the knee and for an irritated nerve in the spine to refer pain into the knee area.
How do Total Knee Replacements Work?
When performing a knee replacement, the surgeon uses a set of jigs and instruments to remove the diseased cartilage and small amount of bone underneath the cartilage. Normally, the cartilage is about 4-7 millimeters thick, and the thickest resection is around 8-10 millimeters. Most people envision a much more aggressive bone removal than what actually happens. Preoperative planning and intraoperative measurements are made to determine the appropriate size and position of the 3 components of the knee replacement- femur, tibia, and patella. This can be accomplished with or without the use of computer assistance, and both methods work well, one is not superior to the other.
Almost every total knee replacement is done using bone cement to fix the components to each bone. All of the muscles, tendons, and most of the ligaments are retained during the surgery. Care is taken to balance these tissues throughout the case by adjusting the component size and position and by utilizing specific soft tissue releases. It is important to know that even the most modern total knee replacement, done with updated techniques, still does not completely recreate the complex mechanics of the human knee.