As if anyone on this site needed another justification for lightening up their load, I was just watching CNN's Fit Nation something or other and they said the following: A 1 pound gain in body weight puts an additional 4 pounds of pressure on the knee when walking.
So, assuming you carried a traditional 45 lb pack, you would be putting an extra 180 pounds of stress on your knees. If you then lightened up and carried a modest 20 lb load (80 pounds of stress on the knees), you would in effect be taking 100 pounds of stress off your knees. Pretty cool.
