My situation was the opposite-- soreness on the outside of the knees, sort of along the edge of the kneecap. Went to +12mm spindles, knee pain completely gone. I had previously mounted the cleats on the shoes as far inward as possible, and it still wasn't enough. Now the cleats are about 1mm outside of center, leaving me ~5mm of adjustment in either direction. I guess it's kinda lucky my knees don't like a narrow Q-factor-- because my EU49 feet wouldn't be very happy banging into the chainstays or pedaling heels out like a pigeon.