Do you know what might have started the shoulder pain? This alone will not indicate a specific diagnosis without a full examination or evaluation. However, it is useful with figuring out if the cause of the pain is something a physical therapist can treat. There are some pathologies that can be referred to the shoulder that a physical therapist is unable to treat. I am not suggesting that you have such a pathology, but what you have should be something a physical therapist should be able to determine if it is something they are able to treat or not. If the PT is unable to treat it, they will refer you to someone that can. I also second what was said above. I don't often advise that patients get an MRI unless necessary, as MRI often shows abnormalities that do not cause pain or show no abnormalities that do cause pain. If an abnormality is not seen, this can either cause or increase psychological pain for the patient. In any event, if you do have something a PT can treat, they should most likely be able to determine the cause of your pain even with no results from the MRI.