I recently watched a video on the tube that discussed the relationship between the crank length and the top of the peddle travel. According to the bike fit guy the angle of the knee at the top of the stroke is important to the power you can safely produce without causing an issue in the knee. I am 5'7" with a long torso and short legs so I will be looking into the validity of the crank length soon. I am going to change the BB and crank as soon as I can figure out what I need. My knees are starting to tell me they are not happy and I am not sure what direction I should go in if any. At 71 there are a lot of other things in play.
Be safe all, Frank.