Well I think it's pretty much established at this point that Jon Jones has a pretty ridiculous list of moves he's willing to break out during a fight.  And just when I thought I was getting the hang of this MMA thing, he pulls out something I've never heard of.  So in the interest of increasing my knowledge base I have a question for the smart people here at BE.

What is a "Wing Chun knee kick"?

I have a pretty good understanding of what Wing Chun is thanks to wikipedia but the internet hasn't been as helpful in explaining the move itself.  Any help is appreciated.