Tim Kisner, an American teammate of Koponen's, has been nice enough to give us some insider insight on the situation:
"He did suffer a concussion. From the sounds of it, kind of like a football player concussion. Remember, Doctors in Europe are much more cautious than ours I have come to find out. He is doing fine now, no problems, so I think he will miss about a week and he missed one game so that will be it. Because he is in the army though, and cannot play, he has to stay in the army full time now until he can play. So not really nice for him. He feels fine they just want him to avoid contact for a few days."
Good to hear he's ok. Interesting that he can get a break from his military service only when he's actually playing in games. Looks like its back to the barracks and ski-warfare until he can resume jump shots.