My right shoulder has periodically felt some pain when getting the bar on my back when setting up for low bar squats. This occasionally cropped up during curls too. However, it's been rather persistent the last few months, causing pain during all arm exercises, and has started affecting everyday life, not just lifting.
Yesterday, I saw an orthopedist, and I failed the Empty Can Test or Jobe Test. With my arm raised to the side and thumb pointed down, I couldn't resist even slight downward pressure. It hurt a little bit, but it was really just extreme weakness. When he did the same to my left arm, it was trivial to resist the downward pressure.
Since I don't remember a traumatic event to suggest a rotator cuff tear, he prescribed physical therapy and a follow-up in two months, at which time I'll get an MRI if it's not fixed. I wish I could get the MRI now, but I understand why he didn't want to. Sometimes things show up on imaging that aren't relevant, so one ends up treating the wrong thing. Conservative treatment is best at first, but I hate the waiting.
I did get a cortisone shot which made it feel about 10 times worse until this morning.
So I may have a torn or partially torn rotator cuff or just bursitis.