Injured shoulder

The night after trying snowboarding for the first time, I headed to bed early -- I was pretty zonked. I woke up in the middle of the night with a very very sore shoulder. Where it came from I don't know, but when I got up in the morning I couldn't even hold my left arm in front of my body. Something was very wrong. I visited my chiropractor on Monday and he was baffled too, but over the next two weeks it has gotten much better and I now have most of my range of motion back. The shoulder is still weak and a little sore when I hold my arm up and to the side, but hopefully it will be back to 100% soon. When it's back in action, I think I'll slowly start back into the pushups.