Funny your doc discussed referring you to pain management and you posted on this today, as I am at a pain management seminar right now.
He asked a question that I will try to answer. These are general comments and not meant to address any specific patient issues.
It is unfortunate that your primary care doc doesn't do injections. This is certainly something that many primary care docs do. I wouldn't refer a patient to pain managment for this type of issue. Most pain management specialist focus on chronic pain issues and don't work with specific limited pain issues such at rotator cuff tendonitis. If I thought my patient needed an injection and I couldn't do it, I would consider referral to ortho/sports med/physiatry.
Consider the ortho referral (or a sports med doc such as I) as your doc may not be as familiar with the treatment modalities or alternative diagnoses to be considered. If he doesn't do joint injections, and shoulders are very easy, his level of interest in ortho/sports med issues may not be high enough to keep him up on these.
For years I thought I had rotator cuff issues in my left shoulder and did rotator cuff exercises out the wazzoo and had intermittent responses and flares. Primarily, as I look back, I just limited the activities that hurt. I can't work overhead for more than a few minutes at a time.
Finally, I got tired of these limits and went to see my neighborhood orthopedist. I knew I didn't have a rotator cuff tear, as there was no weakness, just pain. After a good exam, he diagnosed me with inflammation in my AC (acromio-clavicular) joint. He injected that joint and I was relatively pain free for several months. The AC joint is just toward the midline from the shoulder, where the end of the clavicle (collar bone) meets a part of the scapula.
The pain is starting to bother me again and I will probably seek another injection soon. Sometimes 2 or 3 injections will resolve the issue permanently. Occasionally, surgery is required.
I don't know any details regarding the problems TWM is having, but I wouldn't send a patient to MRI unless he had failed more conservative therapy or I had a very clear idea that there was a problem that was going to require surgery.
Conservative therapy for rotator cuff tendonitis or mild to moderate rotator cuff tear would involve ice, analgesics (NSAID's or Tylenol) and exercise. Frequently, especially if the doc isn't familiar with sports med, referral to physical therapy can teach specific exercises to rehab the shoulder.
If anyone has questions, feel free to comment or e-mail me. I can discuss general issues of disease/injury, even if I can't provide specific diagnosis and treatment over the internet.