Hello @whitewords, I would like to add my welcome to Connect along with @lonna66 and others. Sorry to hear you are having burning pain after your second knee replacement. 6 weeks is still seems a little early in the recovery process but there should be something that will help with the burning pain at night. There have been quite a few other members who have had similar symptoms following a TKR and may have some suggestions. You might find the following discussion helpful:
-- Post TKR. Experiencing stiffness, swelling, burning pain: https://connect.mayoclinic.org/discussion/post-tkr-experiencing-stiffness-swelling-burning-pain/.

Here's a search list of comments from other members who have mentioned burning symptoms following a TKR - https://connect.mayoclinic.org/search/comments/?search=burning%20after%20TKR.

Do you still have a lot of swelling and redness around the knee?