I've long suspected that Knee-Over-The-Pedal-Spindle as measured with a plumb line has no basis in real science. Keith Bontrager's essay pretty much confirmed this for me. http://sheldonbrown.com/kops.html That aside, does anyone know where exactly are we supposed to hold the plumb line? The leading edge of the knee cap does not seem to be the mechanical center or fulcrum of the knee and neither does the Tibial Tuberosity below the knee cap. I find that pretty much anywhere I hang that pendulum on my knee, the line falls very close to the pedal spindle. That is true on a road, track, and CX bike with three different crank arm lengths and differing seat setbacks. If the "correct" position of that line is a matter of millimeters, then the point where the plumb line originates needs to also be exact. I am really wondering HOW to assess the bio-mechanical impact i.e., what is most efficient and least likely to injure?