....... and Q factor. Getting a low Q-factor cleared up all my knee problems (pain from front inside) once and for all.
Getting the right
q-factor is far far far more important than getting a low one.
Not much to add to that lot up there, saddle position (fore/aft/height), cleat position (fore/aft/rotation) have you used SPDs before? Mate has just had reconstructive surgery after several years of using a badly positioned cleat on one foot, never spoke to anyone about the pain until he could barely walk, thought it was normal
. (His coach needs a good kicking, but that's another story!)
If its just started after getting on a new bike, and you ride elsewhere (mtb, for example) it should be easy to find the root cause. The recovery from the damage you've done will be what takes the time.
If you do decide to go down the root of getting fitted, get some advice as to who and go and see. A good number of bike fitters are charlatans interested in no more than taking money off you. As can be seen at sportives across the globe......