@richardrodgers, my first thought, based on my experience alone, is that you likely were given an antibiotic during your second knee surgery that caused your neuropathy. Just a guess, of course and will never be determined.
The reason I say this is that my neuropathy began after hip replacement surgery. The first hip was fine, but after the second hip (same doctor) my neuropathy began. It has affected both sides, but is a little worse on that second side.
No doctor has ever committed to giving a reason for the condition, but one said that the mechanics of the surgery itself was not likely the cause. Later, I was able to find in my medical records what antibiotics were used and while I can't remember exactly with it was, I noted that it was a suspected issue.
If I were to suggest anything, it would be to consider the basic supplements which are recommended (even by my neurologist!) for keeping your nerves healthy: R-Alpha Lipoic Acid, B-12, Benfotiamine (B1), Acetyl-L-Carnitine and Magnesium. I also found Lion's Mane to be helpful, as well as your basics like Omega 3's and Co-Q-10. Getting tested for levels of deficiency might be a good idea as some of these supplements do no good unless you are deficient.