I'm going through a similar problem with the taper. I went from 20 mg down to 10 with no pain at all. At 8 mg I had some pain but wasn't sure if it was PMR or pre-existing back and neck pain. I continued the taper on down to 6 mg at 1 mg drop every 3 weeks. Then the pain got worse and radiated outward into my shoulders. I called my doctor and he told me to go back up to 9 where I had been pain-free. That only partially helped so he told me to bump up to 10. Pain relief is fairly good there. I've learned to take my symptoms seriously and that trying to endure pain does not help in the process of getting off prednisone. I've done research online about the taper. American College of Rheumatology (2015) recommends 1 mg drop per month of prednisone below 10 mg. My rheumatologist says 1 mg every 3 weeks from 10 mg to 5 mg and then a slower taper, but he didn't give details about that. At this point 5 mg seems a long way off!