PMR and preexisting knee pain

Yes, similar. I experience more PMR symptoms in places that have had a previous injury. Not perfectly bi-lateral.

Yes, this happened to me. I had surgery in my left knee years ago. It became very swollen, hot and painful after my covid vaccine and pain in the vaccinated arm did not go away after the expected two days . Had mild osteoarthritis in that knee for some time. After that my left arm and shoulder became stiff and painful and then it moved to right arm and shoulder.

Before I got PMR, I had a lot of orthopedic surgery (shoulder, knee, ankle, wrist), a result of playing a lot of tennis. Thus, I had some aches and pains that were just part of my life. When I got PMR, it was almost entirely in my legs and hips. I was surprised that my shoulders were not affected. Once I started taking prednisone for PMR, the pains went away. When my tapering got below 6-7 mg of prednisone, my old aches and pains returned, notably in my knees. But, the kind of pain was more like what I had experienced before PMR than the kind of pain and stiffness PMR produced. I suspect that this is just because prednisone was no longer masking my osteoarthritis. I take some anti-inflammatory meds (like Omega 3s) for it, but I’ve continued to taper off prednisone. When I first reduce a dose, I do feel some PMR-type pain and stiffness (not severe), but it eventually goes away and, when I feel safe, I reduce again. So far, this has worked for me.

Definitely. As part of my PMR treatment the rheumatologist ordered spinal and cervical X-rays along with blood work to check for rheumatoid arthritis. The X-rays showed mild degenerative disc disease in my neck and osteoarthritis in my lower spine. These 2 areas were always more painful than anywhere else. The neck pain was especially debilitating because at time I couldn’t turn my head more than a few degrees. I’m currently in remission and am slowly regaining strength in both my neck & back but it’s slow going.

I have come to the conclusion a couple of things that have helped with pre-existing injuries/conditions that are exaggerated by PMR:
1) The body's Facia is a natural "body sock" that starts out as a containment for muscles to slide against each other. With each injury facia adhesions builds up and adheres to the muscle, and constrains movement to some extent. And when we have constrained movement, we compensate with counter movements that create even more facia build up.
There is a type of physical therapy called "Rolfing" that has been amazing relief for me for movement restrictions and soreness caused by sports and industrial body traumas. It's expensive and not covered by Medicare so I go only when I really need it and can afford it.
How it relates to PMR for me is certainly it reduces the extent of pain with PMR "flares" ..... But more importantly I believe reducing the facia adhesions assists dramatically in the extent of time painful aches last during a flare.

2) Obviously Rolfing is not available or attractive to everyone (I can only afford it about once a year).... But what I learned with PMR is the importance of keeping the muscles SUPPLE. And this dramatically reduces the extent and the duration of muscle aches when my PMR flares.
I do this with very basic/modified yoga exercise right before bed (middle of the night is when I get the worst flares, and it almost always when I skip evening yoga). I try to get as much morning sunlight on my skin as is reasonable for the temperature, combined with some movement (walking or doing something in my backyard). And I take a Collagen supplement with my protein shake daily. If you're over 70 like me, I take in a huge amount of protein and try to get as much leafy greens in my diet as possible.
I lost a lot of muscle mass with the onset of PMR (plus 60 lbs I found not afford to lose!)... And for my ego getting back the muscle mass was important.... I found that minimizing the suffering from PMR,.even if we can't perform activities as well or at all that we used to ....is directly connected to the health and suppleness of the muscles