WW…Don’t believe that’s an aging issue. But Drs. Aren’t going to have much good imput for you. Best guess it’s a virus. I had something similar and I think it came from a tick. We do wood heat cutting logs and stacking. I met another guy who had virtually the same thing. The Drs. Stung him out on meds and and he stabilized there. Barely able to walk and in pain. Very expensive meds! I never went to the Drs. My cure was hot baths and msm. You can get over it. Work on the immune system and resist. The alternative is becoming an invalid. It’s really painful though. For awhile I couldnt get comfortable in any position. And muscle cramps. Heat packs work.