I had this happen to me a couple of years ago. I did exactly the wrong thing in the beginning by immobilising it and not doing any exercise. When I went to an ostiopath, he said what I needed was exercise, and he showed me one particular one, which has given me back complete movement.

Stand with your back against the wall. Lift your arm until it is at a 90degree angle and then raise your forarm until it is perpendicular to the rest of your body. What it looks like is as if you were like this;

I
I      I
I-----I
I
I

You may not be able to get your forearm to lay flat against the wall, but try to gently get it as close to the wall as you can. Do this repeatedly, and over a period of time, you'll be able to have it lie flat against the wall, and for me, when I got to that point I found I have recovered my mobility completely. This did take a long time, so don't push too hard.

Good luck! If this wasn't clear...pm me, and I'll try to explain it better.

..xx..e