"demand for artificial knees"

Telegraph :

"Smith & Nephew said performance was boosted by a weaker dollar and increased demand for artificial knees, an area in which the group has averted controversy over metal-on-metal technology by offering a 30-year guarantee on its products."

I haven't looked at that market for what must be 15 years, but I'm very surprised S&N can turn a profit on artificial knees, given what was the extremely low cost of a knee transplant from a primate donor.

I wonder if the animal rights campaigners have stopped the trade, because certainly in those days you could get two ape-knees for a penny.