What's wrong this chicken's neck?

I have a barred rock that presented like this:


it did not have any respiratory symptoms that i could tell. it did appear to be in considerable pain and did not leave the coop, which is odd. the bird appeared and acted normal just last night. my initial though was trauma, so i culled the bird based on that assumption and that it appeared to be in pain. does anyone have an idea what else it could have been?

thanks in advance