Cold will bother your knee, I suspect. Just today Mr. Shoes, who still has his original knees, was telling me how much the bitter cold made HIS knees ache after he'd been out shoveling. Which reminded me of something we used to say (and maybe still do say) in Wisconsin about "bone-aching cold," i.e. cold so strong it makes your bones ache. It could well be that the metal in a replaced knee, especially if front and center like with your PKR, could chill a little more than natural bone.
I have noticed with my replacements that if I ice a long time now --I'm eight months out and hardly ever ice anymore-- my knees complain and tell me to stop. They get too cold. That never happened when I was in early recovery. My knees ran "hot" from post-surgical inflammation and never cooled down quite as much as they do now. I have found on recent very cold walks ( in 10 degrees and -10 windchill) that my knees by the end of the walk were starting to say "too cold, too cold... we're feeling it."