Having same problem with rt knee for a couple of months and also discovered slight leg length discrepancy (longer on rt side), probably exacerbated by my purchase last Fall of a mtn bike with longer crank arms (175) than my normal road bike (170), and using it on the street for long rides. Because that increases flexion at top of pedal stroke, it adds to stress on the knee, and I even discovered that my rt knee was kicking out slightly at the top of the pedal stroke. So I stopped riding the long arm bike, started doing the leg kick exercises and have been avoiding all high-gear pushing for a month. Just easy rides, and almost back to normal, thank God.