if there is one thing that shows up in differences between "roadies" and "tourers" (I use this loosely, more to show a point) is that I find there's sometimes a fair amount of snobbery or bragging about gearing. That low gearing means you are, dunno, a wuss, HTFU and all that. Yes, a compact with a bike that weighs 10, 20, or 50 lbs lighter than what I usually ride (a 25lb cross) or a touring bike with loads of crap on it, will be rideable up steep hills--but a well setup triple still shifts fine (imo of course) and allows you to have a higher cadence on a 30 rather than a 34. Especially when you are pooped, or you have a pannier on your bike or whatever.
I dont buy the pt of view that a triple will mean it will make you a weaker climber, I find that over the season, I get stronger anyway, so I just go up a gear or two than I did earlier in the season, and especially as you asked about knees, I think long-term it is worth it being easier on your knees and listening to what they say--and having lower gearing allows you to have higher cadence, which is absolutely better for your knees long term.

the triple works for you, and the weight diff to a compact is really not an issue. Part of it too is where you ride, what sort of hills you deal with.