There are loads of specific crit references to "Strike to arm, if no armor, arm severed, if metal armor, bruised arm -20, if non metal armor deep cut, bleed 4/round."
That kind of thing. . .along with many similar helmet situational critical results. I love those. . .in fact, if I had any say, I'd put one of those into every critical box.
On the other hand, there was an optional rule in RM2 that allowed greaves to negate crits to the limbs. . .it's in the "Q&A" section of RM2 CL.