Thanks for the link...that was a helpful thread and very interesting. I do have mostly symmetrical joint pain, but this particular one is left only, so I'm not sure what to think about it. My doctors don't seem sure either. At first it just felt like knotted up muscles in my upper back, but muscle relaxers have done nothing for it. Then the pain got worse, and I wonder if it could be nerve pain or a pinched nerve or something.
I did think of the heart possibility, but it really doesn't seem like that kind of pain since the shoulder joint seems inflamed and sore/painful to the touch. Also, i haven't had any other heart symptoms like lightheadedness, nausea, claminess, etc. My rheum. did do a chest x-ray to make sure it wasn't my lungs. For now I'm just on pain pills, but if it doesn't subside soon, I'd like to figure out what is causing it and try to treat the the cause instead of just easing the symptoms. Sometimes it does feel like something is going to explode under my arm, but the doc didn't feel any nodules or anything.