Section: Articles by Clinicians

What the Heck Is a Total Knee Replacement?

What the Heck Is a Total Knee Replacement?

What is total knee replacement (TKR) exactly? If you are looking for a medical textbook definition, stop reading because you might be upset. My goal is an easy-to-understand, conceptual explanation. This means avoiding medical jargon that even some doctors find confusing—and maybe even making a car reference.

Let’s start with a simple fact: Knees bend. When knees bend during walking, bones must glide on one another to produce movement.

If you have ever rubbed your hands together really fast (think of Mr. Miyagi healing the injured Karate Kid), friction and heat are produced, and if you keep going you will injure your skin, producing pain. Now imagine if your knees produced this amount of friction when the bones glide against one another during bending. You would not get far before your knees started burning!

Why doesn’t this happen? The answer is: articular cartilage (AC). OK, it’s medical jargon, but it’s necessary because it’s crucial to understanding a TKR. AC provides a virtually frictionless surface for the bones of the knee to glide during bending without producing friction, heat, or pain. In fact, there is less friction in your knees during bending than there is between two pieces of ice sliding across each other. Amazing, right? Sorry about that nerdy moment, but this is why you can bend your knees, walk, or run without injury or pain.

Here is where we get into problems. If you start losing your AC, commonly due to age and “wear and tear” (called osteoarthritis), you can start having pain. Once you lose a significant amount of AC and have pain affecting the quality of your life, even after conservative treatment, your doctor may recommend a TKR.

So what the heck is a TKR? Think of how we reached this point. We lost our AC, which causes pain. Currently we don’t have the ability to regenerate AC lost from osteoarthritis. We can only replace it with an artificial surface. During a TKR, all we are doing is removing the worn out AC and replacing it with new artificial materials (metal alloys and polyethylene) that reduce friction. We don’t change the muscles powering your knee or the major ligaments that provide stability. Nor do we remove large amounts of bone. We merely replace what was lost and restore balance to your knee. Simply put, a TKR is like changing the tread on your car’s tire.

Dr. Corrales specializes in the management and surgical treatment of degenerative and arthritic conditions of the shoulder, hip and knee. To schedule an appointment with Dr. Corrales, call 909/593-7437. Check out our Revive Joint Replacement Program for more information.