I read your post and can really feel for ya. I am almost 14 days out from my 4th TKR on the same knee. I too am experiencing that on-fire burning sensation. I had it with the other three surgeries but not as bad as this time.

When I discussed it with my new and greatly improved surgeon he said it's most likely from nerve damage. I had my shoulder replaced and experienced the same burning. I've been taking Gabapentin three times a day and it helps some. Pain meds do nothing for this type of pain, you've probably found that out. My situation is improving a little every day.

The only advice/encouragement I can
give you is to not give up. Hang-in with your P.T. and keep your knee moving. You will be successful if you don't quit.

All the best!