If you are looking for a medical textbook explanation, stop reading because you might be upset. My goal is an easy-to-understand conceptual explanation for a total knee replacement (TKR). This means avoiding medical jargon even 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) you realize 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 during bending when the bones glide (rub) against one another. You would not get far before your knees started hurting or perhaps caught on fire!
Source: WestCoast Magazines