Firstly, I know I must see my GP and I will do so in early April, I'm away from home (in a different country) till then.
Ten years ago I had a bad accident, which resulted in an operation, a humeral prosthesis and three months of rehabilitation until the nerve damage was reversed. The rotator cuff was badly damaged too. I have some limitations of movement in that arm (can't raise it in front of me above shoulder height) but have never had pain and I've been extremely happy with all the medical care I received (in France).
Now I am beginning to get the odd twinge at the top of my arm with small movements and I'm worried that the prosthesis is beginning to fail. Dr Google tells me that it's a possibility, but on the other hand it might just be age-related arthritic type pain. (I'm 73, extremely fit and healthy and have an active life).
Obviously this is a pretty specialised question but with MN you never know who's reading! so I thought I'd try.