Question
I am a gymnastics coach.  Over a month ago I was spotting a gymnast on a skill that required me to move my slightly bent arms from in front of my body to the left side.  My left arm ends in a 90 degree position with the elbow about mid rib level and the entire arm slightly behind my shoulder.  I felt a sharp pain like a pinched nerve would feel like in the back.  (I don't know if that is a real condition but I assume you've heard that explanation of pain a lot from us general folk. lol.  

Ever since then when I move my arm behind my head from above I get the same sharp pain.  Sleeping on that side is also painful so I don't.  Holding my arm out to the side straight or bent is very painful but swinging it forward and backwards is fine. I don't experience any pain forwards.  However putting on a shirt or jacket is very painful.

The pain is sharp and in the rear of the deltoid muscle.  Did I pull a muscle?  I have laid completely off of it however it is not getting any better.  What can I do?

Thanks for your help!

Answer
Ray,
First of all, thank you for the details on how the incident happened. Also, your detailed explanation of which motions and positions increases pain is helpful. When you say it hurts behind the deltoid, I will assume you also have pain on top of the shoulder (called your AC joint). Your AC joint is a little bone like protuberance on the top of your shoulder. If your shoulder hurts when laterally raising the shoulder and not on flexion and extension, then it is most likely an AC joint subluxation (misalignment). It could also be shoulder impingement syndrome or it could be a muscle sprain/strain. A muscle sprain should improve (after 3-4 weeks)after ice for 3 days, then heat. If its still bothering you with little or no improvement, then I would consult a sports chiropractor. If you just want symptom relief then take ibuprofen over the counter. If you don't like to take medication and really want to get to the cause of this injury so you don't have chronic shoulder problems i would see a sports chiro or sports medicine physician.
obviously i can't diagnose over the internet with out seeing you but that would be where i would be leaning towards.
good luck!