You're probably right about the shoulder muscles, I'm making a conscious effort to avoid that now. (Having said that, the first time it happened was the day after the operation while I was sitting up in bed. I'll ask the doc at my assessment on Thursday.) In the days immediately after the plate was inserted I had rotten pain if I let the arm hang its weight by itself. That felt as though I had a 10kg dead weight hanging on a nail through my shoulder bone. I have been attempting to taper off the cocodamol as I'm wary of being dependent on it for too long. It's good for the pain that would keep me awake but does little for the underlying, constant ache and general discomfort, so I only take it when I need to.