Thanks for posting that.
I actually had the first one of my players actually have a concussion. It was in one of our practices, and because I was unhappy as to how hard my team was (or rather, wasn't) running in the last game, we made every possession a running drill - after a change of possession or a made basket, offense had to touch the baseline and then the half-court line before receiving the basketball to put it into play, and defense had to touch the half-court line and then the baseline before they were allowed to play defense.
One of my young men became confused about which line he was supposed to touch first, ran a couple of steps in the wrong direction, and turned backward immediately - right into the path of an oncoming player. He took the hit, stood there for a second, and then collapsed. We had to take him to the emergency room, where he was diagnosed with a concussion. Nasty stuff. Cost him a missed practice and a missed game. Had his best shooting game his game back, though.
For me, the injuries are usually twisted ankles, although I've had a dislocation, ligament damage, cartillage tears, and assorted jammed fingers and floorburned knees. Worst of all was a muscle tear, which caused me to miss half of my 9th grade season.