I am 5'9", 31-31.5 true inseam. I was fitted to a '05 21" trek 520 by my LBS (actually, it was the only one they had in stock). The front of my knees hurt, just behind the kneecap. To relieve the pain, I tend to move my hips backwards away from the handle bars. My seat is at the correct height according to all the normal advice. This bike hurts my knees. I use granny gears all the time and avoid 'pumping' now, but everytime I get on this bike, I get off with sore knees. I can't get comfortable and I don't enjoy this bike anymore. Maybe I have the wrong size (too small)? And, of course, I can't raise the handlebars because the fork has already been cut. I have well fitted shoes, knee savers, and speedplay frogs for this bike and another. I don't think clipless setup is the problem because my other bike doesn't hurt at all (an older schwinn).

Can people tell me what size they are and what size trek 520 they ride? Any suggestions on the knee issue?