I had bilateral medial hemi knee replacements about 8 months ago...one knee is a real gem, very little pain, great ROM, the other has been not so wonderful. Just thinking about your 'cold' issue...my knees don't like being cold. The nerves around my knees are not fully recovered yet (wonder if they ever will), and I wonder if lack of nerves enhance the cold feelings you may have. Happy to chat more if you want to.
BTW, I'm female, 53, and back to cycling (50k road rides and some MTbiking), gyming, swimming, yoga, gardening, and walking.