Ie: a 200 pound person exerts 300 pounds on each knee joint. Is it something to do with gravity or the physical force exerted when walking? So does that mean a 600 lb withstands 900 pounds of force on each knee?
In: Physics
If you were standing still on one leg, one knee would be supporting the weight of your body (less the lower leg and foot below the knee). To move, you have to exert *more* force — first to push your body with one leg, and then to catch yourself with the other leg a pace later.
The knee and leg bones are levers. The muscles (and tendons and stuff) pull on part of the leg bone near the pivot point (knee) while the part of the bone further away the pivot point (foot) needs to support and move the body’s weight. The part near the pivot moves less distance than the foot itself, but the muscle needs to transfer all that energy down to the foot, so you need to apply more force (but with less actual movement) to transfer that amount of energy.
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