Knockdown Recovery is a survival gear perk that gets you back on your feet faster after you are knocked down. It cuts the dangerous moment when you cannot act.
When an explosion or heavy hit knocks you over, you recover more quickly. You get back into cover or return fire sooner.
Situational. It helps in rocket-heavy fights, but a speed boot perk is more useful most of the time.
Major Blast Protection or Heat Stress cut the damage from the blasts that knock you down.