That truly is an interesting question. My opinion is PMR causes "systemic inflammation." Most of the "PMR inflammation" is confined to specific areas of the body and only attacks certain tissues.

The "generalized inflammation" by its very nature can attack anywhere it wants to. It is carried in the blood stream and floats around looking for things to correct. I don't think inflammation just "selectively" looks for specific areas in the sense that PMR only attacks certain areas. Prior injuries would likely be areas where the immune system would think may need some additional work.

I had an old sports injury to my right knee that "bothered me" all my life. The knee pain I felt was definitely more during my PMR years. I had to get my knee replaced. My logic was maybe a knee replacement would help me reduce my prednisone dose. After my knee replacement surgery I was able to reduce my prednisone but still could not taper off Prednisone entirely.