I am so sorry I am just reading your recovery thread. I'm now 7.5 wks post-op from my right TKR and not online as often.
I know the burning/stinging pain next to the incision very well though. When my initial dressing was first removed by the Home health nurse on Day 3, she commented how the areas on both sides of my incision looked as if severely sunburned. It worried her. I had to speak to my surgeon on Day 5, as the pain kept worsening, and it turned out I did have a severe inflammatory reaction to the surgery. My surgeon put me on full bed rest until Day 8-9---only bathroom trips allowed and NO PT of any kind. I also ended up with an unusual complication known as fracture blisters because of the swelling. The worst of the fracture blisters were located on those reddish "burn-like" areas, and each area was about 2.5 long by 2.5 inchs wide, but on BOTH sides of the incision.
She told me to keep close watch to see if the redness worsened, and to call if anything changed. Luckily the redness did NOT get worse, even though the fracture blisters continued forming through Day 5-6. The surgeon wasn't worried though, as the redness never spread. It was a rough couple of weeks though, and the pain meds barely took the edge off, even at high doses.
Even now though, these are the most sensitive and sore areas of my knee----not the kneecap, not the incision, and not the muscles around the knee----but those areas that had the "sunburn" and fracture blisters.


It makes me suspect that's where most of the mechanical work in the knee was done during surgery. I plan on asking my surgeon at my 8 wk follow-up, as I forgot last time. I know I had large bone spurs removed from both sides, and the boney "knobs" are now gone, giving my knee a whole new profile---but those are the "burned" areas too. I can't help but think it's all related.