Your knee is a living, biologically active organ. Cartilage is maintained by cells that respond to their chemical environment, and the primary driver of OA progression is not mechanical grinding.
It is chronic, low-grade inflammation that poisons the environment in which those cells are living.
So we need to stop thinking mechanically and start thinking more biologically. Our cartilage responds favorably to the same stimuli that improve our overall health and wellness.
This is precisely why high intensity exercise in moderate OA (grade 3 of 4) decreases pain and actually increases cartilage thickness.