@dabshire @johnbishop I have had TKRs on both knees, and prior to that had meniscus surgery on both. I have never had a problem similar to your experience.
Since the stinging and numbness is in both feet I don't see how it could be related to surgery on one knee, unless your gait has altered in such a way that it is causing a foot problem. Frankly, though I think that's probably a stretch but it does seem odd that it started after the knee surgery.
I will be looking forward to hearing what your primary has to say about it.
JK