Doh! I never considered that the lunges could be the problem. I assumed that a fit person with no history of knee problems "should" be able to do them.

I actually like lunges for their efficiency. We do A LOT of them in class with compound, upper body, exercises. I'm going to substitute other lower body movements for a month, though, and give my knee a break. I'll give up lunges entirely if they still make my knee hurt after the break. I'll leave my saddle height where it is in the mean time as my knee doesn't hurt during any other activities.

Thanks for the input Sky and Oak.