I recently went on a short overnight tour and have never had issues with my knees before. So to get a few things out of the way:

-I've never done more than a 3 day tour
-I've ridden a unicycle and bicycle over 100 miles within a day or two and have never experienced knee pain before
-I am getting back into cycling after a year of not riding, but have been riding about 5-10 miles a day before this tour
-I have ridden in cold weather with no pain as well

Even on this trip, no problems the first full day, I felt fine until about 30 miles in on the second day. Then I started to feel effects that seem to coincide with the description of Chondromalacia. Knee pain in the front of the kneecap. It quickly began to become pretty intense, but I couldn't stop that day as I was on a time constraint. After a week of not riding I felt fine and got back on the bike....the pain immediately and sharply came back within a mile or two. Now I'm looking up ways to get back to normal through exercises, but I'm concerned because I haven't had any issues with my knees before, even when I was running and rather abusive to them.

I have noted 2 things that were different:

-I was wearing long compression pants (because it was cold)
-It was a hard-pack gravel Trail

According to Sheldon Brown's website this kind of injury can be caused by twisting or lateral forces on the knee. Is it possible that compression wear could put pressure in the wrong spot while cycling? Is it possible that a different terrain may have changed my riding form in a way I wasn't aware of that could have caused this?

Any and all thoughts are welcome. I'm rather frustrated I haven't been able to commute even 2 miles to school over the past week or two. I just want to make sure this kind of thing doesn't happen again, especially if I go on a larger tour.