say if you where to hit someone in the arm thier arm would cripple like on FO and if you hit people in different places it will do different amounts of damage e.g. if i where to fire an arrow in someones head it does more damage than hitting them in the arm or in the knee (lolz) or hitting them in the head it will be an instant kill because no1 survives that, the point is that they needed to add the injury feature from FO because that adds a sence on realism and will make roleplaying better.
This has been proven false time and time again throughout history.
Also, knee-shots immediately take you out of the fight. If you're lucky, you become a guard. If you're unlucky, you die.