Can't rotate arm so palm faces up?

I don't know when it started, but if i hold my arm out straight palm down and attempt to rotate my arm 180 degrees so the palm faces up (from shoulder joint, ebow locked), I can only get it around about 100-120 degrees, it is worst in my left arm. I injured my rotator cuff a few months ago because my chest muscles are too strong for my back muscles, so I've pretty much stopped with chest stuff and am focusing on back. I still feel a disproportinate burn in one of my shoulders when lifting weights which recruit these muscles. I asked a physiotherpist at work about it and he said something, but I wasn't listening because I was distracted by the fact that he had barbaque sauce smeared all over his mouth. I fell about 10 feet onto ice when I was snowboarding a few years back and didn't have enough speed to clear the flat part of a jump and took a lot of the impact in my arms, I noticed it around then, but as I said I don't know when it actually started. Therefore, I am wondering what is physiologically causing this and what exercizes can I use to fix it. Chur!