Hi Peter,
My late wife took a dive down a staircase about 15 years ago, smashing her right shoulder up so badly that a replacement had to be fitted. It took about 3 months of exercises before a reasonable degree of movement was restored. Not a full range; for example, she could manage a Nazi salute, but couldn't raise her arm much further than that, and often had to get out of her car to collect tickets from car park barriers. Overall, however, the artificial shoulder hardly hampered her at all, and no-one would have known she had one. What always puzzled me was that its construction was basically of metal, but it never set off the alarm at airport security barriers.
The exercises consisted of things like crawling her hand up the wall and pulling at elastic tied to the banisters. I rigged up a pulley over a doorway with a rope over it so she could hold one end in each hand and pull down with her left hand, thus raising her right arm by a little more each day.
Hope this gives you some reassurance.
Andy