Uh.. bone weights?

Hey guys. I’m making some animations to use in a game, and for this certain animation my character’s hand gets mangled like he just put it through a piece of heavy machinery. See?

I’m under the impression that this is caused by bone weights, but despite my efforts in the Weight Painting mode I can’t get it to look right, and what works on one frame looks even worse on a different frame. Halp?