I have a rotator cuff injury as well.
I had nasty, sharp left shoulder pain when lifting my arm straight out, away from my body, starting at about a 45* away from the hip. Avoiding that motion, it was okay, mostly. No definite injury, it just hurt more & more from about June. Like dhartmann34 above, I could still play golf, but it would ache after the game, like it was bruised. And it was starting to affect my swing & scores.
Saw my doctor & xrays showed normal bones with no arthritis, but an ultrasound showed a complete tear of the Supraspinatus component of my Rotator cuff tendons. The shoulder specialist recommended surgical repair - just one hour of keyhole surgery - which he did yesterday (October 4th). Wow - does it ache today!
The real problem is recovery time, slower than grass growing! Six weeks in a sling, with minimal movement - can't even drive (a car!), then six weeks of low stress mobilisation & physio, then another six weeks of strengthening physio - IF EVERYTHING GOES RIGHT.
Hoping to get back on the course sometime in February, but until then, I am an armchair expert on golf!