Thank you both for your comments.

I am in complete agreement that the source of the problem must be treated, not just the pain. I have been reading here and other places on-line, and am more informed about shoulder issues than ever before.

It's the weekend now, and PT begins Monday evening.

Meanwhile, I am practicing pinching my shoulder blades together (which, I'm assuming, means practicing excellent posture) when I reach, sit, drive, etc. As I do that, it's a little uncomfortable (not really painful though) and I feel a "popping" in the scapula area --- I wonder if this hints of instability or weakness in that area. I'm wondering if I should be using my arm at all, or if it is OK to use it (except for the activities that stress it) but only while pinching the shoulder blades.

So, to follow through on your advice: How can I ask my practitioners to check and use your suggestions without sounding like a know-it-all consumer whose head is full of information I get off the internet?