Quote Originally Posted by Biciclista View Post
it's possible my seat has shifted, but yes, i was meticulously measured for crank arm length, all that stuff.
Shorter cranks are just easier on the knees, less leverage & range of motion for the knees. So while you were measured for what should be right - it doesn't mean that shorter cranks wouldn't help. If someone has bad knees to begin with (not that I'm saying you do), regardless of whether they fit 175 mm cranks, smaller cranks are going to be easier on their knees
http://www.roble.net/marquis//crank.length

Maybe just try riding at an easier gear than your normally do for a bit and see if that makes things easier?