Ok, apparently this has nothing at all to do with my pedals - as I rode my horse for 2 1/2 hours yesterday and I had the same problem with my other knee. This is the longest that I've ridden her in about 2 years, most have been short rides and I haven't noticed it. I'll do some digging around the site as I thought I saw some good discussions about knee pain as it relates to problem hips. Thanks for the advice, all!!