Originally Posted by
KnottedYet
If your forefoot doesn't get the weight transfer pattern heel-toe like it does when walking, it doesn't always get set up to be a rigid lever. So it kind of collapses (pronates) throwing your foot/ankle/knee/and sometimes hip out of whack. Sometimes the poor achilles tendon will jump in at this point and try to stabilize the system. Since it really can't do that well, ya get tendonitis and other nasty boogers. (if the achilles doesn't even try, you can end up with knee pain as it is the next joint to take the stress)