I'm not totally ruling out that there is a stick propping up Kahn and that a member of his team took this picture and posted it on Twitter for him. That grin is the same type of grin that someone has when you wake them up in the middle of a drunken stupor. It silently screams "I have absolutely no idea where I am right now". It's very possible that the CTE instantly took over his brain after he got punched into a galaxy far, far away and that smirk is it's way of displaying the pleasure it took in claiming another victim during the NFL offseason.
That being said, it's still a pretty boss move to put on a happy face for the fans after (presumably) laying dead in the middle of a ring just a half hour earlier. Take notes Ronda Rousey. This is how you handle disappointment, not by putting on a ski mask and going into hiding on the highest ledge of a 40 story building for months at a time. I can't say I know all that much about boxing. In fact, I didn't know who Amir Kahn was until I watched 6 second clips of his body turning into a Raggedy Andy doll. I do know that I wouldn't want to be the next person to fight him though. Not when he's all smiles just moments after taking an awe-inspiring knockout punch that would make WorldStar's finest look like a playground pushing match. Safe to say his next opponent won't have the power of Canelo Alvarez, and even that wasn't enough to keep this guy down and out for more than a commercial break. I don't know what his future as a fighter holds, but I feel pretty confident in saying that it includes some rather uneasy competition that fears that they are facing an unbreakable face.