I injured my right shoulder falling off a ski tow. I rehabbed it myself by doing passive range of motion exercises (I prescribe them all the time so I know how they work). After 6-8 weeks it settled down and now I have better range than before the injury (I can reach into the back seat while driving).
A couple of years later, my left shoulder was giving me trouble. There was no injury. The exercises didn't help. I finally saw the physio, who concluded that my shoulder was fine, but my spine was way too stiff, so the shoulder had to work too hard. That time the exercises took a lot longer and it relapses if I forget.
My point (if I have one) is that rotator cuff injuries can often heal if you rehab them correctly from the start.
