With the invent of new surgical techniques and instruments Knee Replacements can now be performed almost like Resurfacing.
Taking as little bone as possible and resurfacing it with the equal amount of metal and plastic.
Total Knee Replacement vs resurfacing
The attached picture is from a knee arthroplasty I performed today. This is the actual picture of the bone cuts I performed on the femur. This was possible due to surgical computer navigation system allowing to reset bone with 5mm accuracy.