I had a partial replacment of my left shoulder in 2008. I needed a new ball not the socket. The PT is strenous, but I kept telling myself "NO pain, no gain!!" I do not have full range of motion, but I have no more pain like I did and for that I am thankful. I can almost get so that my upper are is out straight from my body, but cannot get my arm up the rest of the way. If I take my right arm and help my left arm up, it will go up all the way without any pain. The therapist could not understand why it wouldn't go up all the way. The doctor did not know why either, but wouldn't admit to doing anything wrong either. I could be a lot worse off than I am,so I am thankful. I had bone on bone and a lot of arthritis and spurs.
Good luck. Just do as you are told and don't overdo. If you want to talk, PM me.