I was diagnosed with Polymyalgia two years ago. I was on 20 mg. at the beginning of treatment, but I am currently only taking 2mg of prednisone.
In the past four months, I have
experienced some of what you described. Muscle cramping and spasms in very strange places…like left of my mid-back and lower abdomen. Fortunately, it usually doesn’t last long.
I will ask my excellent Rheumatologist about this strange phenomenon.
Best wishes with your journey.

I ordered some quinine off ebay for muscle cramping. It's related to Hydroxychloroquine, (Plaquenil) and it's an old treatment for cramping. Tonic water does too but it's sugary and I don't use artificial sweeteners.
I dropped half my Plaquenil yesterday and noticed a leg cramp. Some rheumatologists prescribe Plaquenil for PMR as it is "steroid sparing".

I’m so relieved to see that others have fatigue too! I also feel very shaky and unsteady on my feet. Interestingly, my rheumatologist started me on 20 mg of prednisone 20 months ago, and tapered me down to 5 now. I know that’s good, but I’m concerned about this shakiness.
I used to be a walker and a golfer, but can no longer do either!

I’ve been having terrible cramps at night in my feet and calves. My fingers cramp mostly during the day. Talked to my PCP and rheumatologist about it and neither had any ideas or if they did they didn’t share them with me.