I spent a good 7 years wondering what was going on. It started at 45 yo with what I presumed was plantar fascitis. After a stupidly long walk on concrete round my marathon runner friends' home town, I thought I'd never walk normally again.
I then started to get muscle aches so bad I got checked out for RA and other similar medical conditions.
When that came out clear but I was severely deficient in vitamin D, I thought thst must be the reason.
After resolving that and then having another "flare", I tried HRT.
After this didn't work, I gave up trying to find out an answer and resigned myself to decline and pain. It got really bad in 2024, and it started to escalate into full on systemic all over neuropathic pain.
Finally, I had a breakthrough last year - the statins I took for high cholesterol. I stopped taking them and it helped somewhat. Not cured, helped.
Then I was finally diagnosed with hEDS. It's Hypermobility Ehler Danlos Syndrome. I have been on a pain management course, and started taking Duloxetine. It has been life changing. My levels of activity have been gradually increasing towards feeling like a life again.
I'm telling you all this because these were all plausible avenues. I hope you find something useful in it all. I went down a lot of dead ends before useful therapy.
Good luck!!