IDK, but knee replacements are amazingly fast and perfected these days. My dad was walking on said knee within a day when he got the 2nd one replaced a few months back. Drugged up at first of course, but I'm sure he was off the narcotic meds in a few days. Physical therapy is longer though, and possibly the deal breaker is that the flying is probably the worst thing after the surgery. I'm sure it wouldn't affect your flying, but sitting in a cockpit would probably be horrible for the post-surgery knee.

Look up FAA CAMI and put a call in to them. I'm sure they can answer your question.