As a brief followup, the day after that cold, rainy Tour ride both knees were irritated, but it seemed taking a day off had taken care of that. I rode 189 miles the following week, however, and by the end of that time the knee irritation was back in all its full obnoxiousness. Another day off wasn't enough, the knees were felt again, so I took a full five days off the bike this time, which wasn't that hard to do since I had 3 full days of military duty in that time anyhow.

From what I read, riding with cold knees reduces the bloodflow through the joint, and can lead to knee irritation due to underlubrication of the joint. I'm guessing that this is what happened to me. So don't think that rules 5 and 9 make riding under-dressed in bad weather a good idea. I'm about to go out on a 32 miler, it's like 45 degrees outside now, and I'll have leg and arm warmers on this time. It's going to be interesting to see if the five day break was enough for my knees to get back to normal. And this whole thing has taught me a lesson, too, that will influence how I ride for the rest of this winter.