Yes, I believe the effect is that with shorter cranks you always are riding effectively in a lower gear. You can compensate of course by upshifting, but you always have a smaller circle to pedal. If you keep your seat-to-bottom-pedal range the same, your knee angle at the top is eased up.

The key thing with crank length is that a .23" difference is doubled to .46" when you look at the full circle.

What is confusing is that usually the longer lever = more leverage = better.

???

I've been riding 175's and having knee trouble, which nothing seems to fix. I'm probably going to soon try 170. In fact I recently had a rental bike with 165's and that worked out better for me than my current bike.

My beef with crank length is that so few manufacturers list the info on websites. (Kudos to Jamis as one of the only exceptions).