If your knees don't hurt, you might want to just leave it alone. I went through this with Erik Moen, who said my left knee looped out a bit at the top of the pedal stroke. Didn't hurt, though. I made a conscious effort to correct it---and THEN it started to hurt. So now I just let my knee go where it wants to and don't suffer from it at all.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks