take a look at some of the details as well. When the guy drops, he is ushering with his hands, trying to tell the other guy not to hit him. And you can tell the other guy doesn't realise, he just thinks the guy has pussied out. Disturbing shit though, that would be awful, the way he tries standing on it.
Fuck kicking anything, ever.
Unfortunately, that is real and it is something that happens every once in a while in kickboxing or other MMA sports that involve kicking. The guy will either break his ankle kicking the other guy, or the other guy will kick his ankle when there is weight on the ankle and it buckles.
It is much more common for the ankle to crack and to be repaired after the fight, like the time Donovan McNabb (pro american football) broke his ankle and finished a game.