Have you thought about biking? Maybe not a bike itself if you don't have one, but an exercise bike? The impact on your knees from running is far greater than the impact on your knees from cycling, so in theory, you shouldn't get as much of a flare up from cycling, although admittedly, I do not know how bad your flare up is and what movements are most painful. Just a thought, though.

I haven't been keeping up with a lot of posts here, so I can't tell if you have a gym membership or not, but I think an exercise bike might help.