Hmm, I'm going to take a semi-educated guess here after a large number of ortho surgeries, but no TKR. This sounds like nerve regeneration/healing pain, which can go on for quite some time. Nerves are bruised, cut, moved and otherwise insulted during major surgery, and are notoriously slow at healing. After ACL/MCL replacement quite a few years ago, I had intermittent nerve pain for an entire year, which eventually subsided.

If the pain is not disabling or throbbing, especially if it seems to "move around" this is probably what you are experiencing. If your recovery is otherwise going well and you have not had any infections, you can probably just watch it. If you have had complications, have other health conditions, or it seems to be making your recovery go backward, a message to your doc to discuss it would be a good idea.

Good luck, let us know how it goes.
Sue