You possibly need to consider that your high dosage of steroids did have a side effect of depressing your adrenal grands long term. This can cause systemic pain when titrating down off the prednisone that could be confused with PMR pain. Waking up your adrenal glands is a major portion of the steroid triturating process. If they do not wake properly you could have what is known as adrenal insufficiency. This can be identified/eliminated via blood tests. This test must be drawn at the proper time of day, it is a sensitive test, but properly done it will reveal if there is an adrenal problem. Talk with your PCP or Endochronogist about eliminating this as a contributing cause for the steroid titrating pain.
Here is a short Mayo Clinic article on Adrenal Insufficiency https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-understanding-adrenal-insufficiency/