Grumpy post alert. The good thing is that my knees are not giving me any problems. I don't know if it was the month of rest, or that I'm in the small chainring more.
Riding the small chainring more should be easier on your knees (compared to riding the big ring); at least that's how it works for me.
Regarding overall loss of fitness due to business travel, I hear you on that one; been there and done that. When I'm in the U.K. our distributor there loans me a bike to use but other than that I've not been that fortunate. I'm a bit older that you are (64) and a bit lighter (155 lbs.) but overall, loss of fitness due to business travel is brutal for everyone equally!
Rick / OCRR