Summarized from the rules
Elbow drop and kneed drop are committed or all-out attack maneuvers. Committed gives you a -2 penalty to your defense and all out leaves you defenseless. If you hit the enemy gets a chance to defend at -2, parry, block or dodge. If he parries your body counts as a "weapon" with a weight equal to your strength score (average is 10, this means you can blow through or even potentially break lighter weapons), both do equal damage but split in two distinct ways.
Elbow drop can be used on someone who's kneeling, if you cause knockback, they need to make a dexterity roll to not be knocked on their ass, and additionally if you miss, you take damage to your torso equal to what you would have inflicted (this also occurs if you hit his shield) and you end up laying down if you pass or fail.
Knee drop only has the damage apply to one leg if you miss or get blocked, and can only be used against one target and you end up on your knees instead, whether you pass or fail.
They're similar, but not identical maneuvers for use in different situations. Knee drop is also an easier maneuver to pull off, with a higher default, meaning it's easier to train up.>>64941526
See, the thing is, if he actually does have stress boxes, no matter what I throw at him if I roll a 1, 2 or 3 he can still tank that hit, no matter what I throw at him.