I have a rotator cuff injury...
...but mine was a tragic saxophone injury.
I was playing a production of Forum twenty years ago, in a theater with a great orchestra pit. My daughter was sitting next to me on my right, soaking up the musical theater experience, and occasionally helping out with a bad page turn or horn change.
During the "House of Marcus Lycus" number, there was a fast transition between baritone and bass clarinet, this for one of the "between courtesan" vamps. The idea was that she would hold the baritone while I played bass, then have it ready for the next use in a hurry.
The first baritone passage comes and goes, I unhook the horn, cradle the tube in my hand (with the fingers curled around the tube) and move to hand it to her. Unexpectedly, she grabs the horn and rapidly pulls it up and back towards where she was sitting.
My hand, arm and shoulder, with the fingers trapped around the horn, gets jerked back in a hurry. I could feel the tearing going on in my shoulder, and almost had to bite my tongue to stifle the cry of pain, so searing was it.
My daughter realized what happening as soon as it happened, and slacked off almost instantly, but by then the damage was done. The shoulder felt like a knife had been stuck into it for the rest of the evening, and most of the next day. It was a miracle that I didn't drop either the baritone or the bass, which I kept tightly gripped in my left hand.
I put off going to the doctor until the injury stopped hurting. However, that next summer, when I tried to throw a baseball, I discovered that my arm did not work normally any longer. The extent of the injury was that I had trouble elevating the arm above the shoulder, and I could not lift any weight with my arm extended. (With the upper arm pointing down alongside of the body, I can still lift a hundred pound with the lower arm - it's just the extended arm that's the trouble.)
(When I finally got around to visiting an orthopedic surgeon, he said that I had let things go on too long, and that the contracted and atrophied muscle could not be reattached and returned to normal function. There's a moral there somewhere...)
And, other than me missing one of the bass clarinet vamps in "Lycus", I didn't drop a note. What a trooper...