Yes the knuckles are facing the catcher, when my dd throws it, it will curve and drop to the outside on a right handed batter. It is done by flipping the wrist creating backspin on the ball. I don't know how often he threw it, maybe never, I don't know. But with all due respect Rick, you present a lot of good advice and I respect that very much, but that doesn't mean that you know everything. It could be being thrown more often then you think.
Just to clarify what I wrote earlier...I said my DD does not flip her wrist...I would say she rolls her wrist over the ball. So at the end her knuckles do face the catcher.