My experience was the same. Tapering off Prednisone is uncomfortable and painful even when PMR isn't active.

It is very easy to mistake Prednisone withdrawal symptoms for PMR. If you are having withdrawal symptoms your body should adjust to the lower dose of Prednisone after a few days. In the meantime it is uncomfortable but the pain is not as bad as PMR pain. "Niggles" of pain is not a good reason to increase your Prednisone dose. Unfortunately, withdrawal symptoms if they get worse, are treated by increasing your Prednisone dose by 1 mg or 2 mg. A PMR flare might need a bigger increase in dose but that is only when the pain continues to get worse and gets more severe.

I think withdrawal symptoms are usually felt around the 7 mg dose of Prednisone. That is when you probably need to wait and see what happens. You can experience more withdrawal symptoms with every subsequent decrease in your prednisone dose so tapering gets slower and slower if you don't have a PMR flare first.

There is a tipping point when your body just doesn't have enough cortisol from the adrenal glands to offset the decrease in synthetic cortisol from Prednisone. When this happens, the body lacks the ability to regulate inflammation. More stress of any kind be it physical, mental or due to an infection may trigger another flare of PMR or something much worse.

Secondary adrenal insufficiency from long term prednisone use is another beast to slay. It can take a year or longer for adrenal function to improve depending on how long you have been on Prednisone. Sometimes adrenal insufficiency is permanent. I was just lucky my adrenal insufficiency wasn't permanent even though I was on Prednisone for 12 years. In most cases adrenal function will improve as long as you can stay on a lower dose of Prednisone. Adrenal insufficiency is also painful and characterized by overwhelming fatigue.

It took me almost a year to taper from 3 mg to zero simply because my cortisol level was too low. My endocrinologist could only tell me to wait until my cortisol level improved. She said I shouldn't even attempt to taper any lower than 3 mg until my cortisol level increased. As far as I know waiting and checking a cortisol level periodically is the only way to know when your adrenals are able to produce adequate amounts of cortisol again. Waiting that long on 3 mg of Prednisone or less was very difficult for me to do. My endocrinologist wasn't optimistic that my adrenal function would ever improve since I took Prednisone for 12 years.

I think the only reason I didn't have a PMR flare was because I was on a biologic that prevented the inflammation caused by PMR.