Non Weapons Defense

Me:
Well hello there, what happened to your wrist?

38 y/o male patient:
I was in a non weapons combat class and when we use the upper arm block in self defense, we usually hold like this, but I had my hand twisted like this, which is common in law enforcement, so when my partner hit me, my arm went down instead of out and she hit me so hard that something popped and it started swelling.