Knee Replacement: A Merchant's View

In a knee replacement, our human knees have three surfaces that rub against each other and articulate. Oftentimes we don't resurface that patella. We don't cut off the nature's good cartilage to put our plastic piece of almost cartilage on there. And over seven years, that can wear as it rubs against the metal of the femur covering. So you can go from having a normal asymptomatic healthy layer of cartilage on the patella in seven years to wearing it down to bone of the patellA rubbing against metal.