I’m 38 and this sounds like me. Mine are all old military injuries coming back to bite me.
I’m plagued with calcific tendinosis in both Achilles and rampant osteoarthritis (my cartilage is dissolving systemically throughout my entire body). Had over an inch of bone spur removed from my left shoulder (acromion)/collapsed AC joint/supraspinatus tear, right shoulder is getting the same treatment in the 2nd week of Jan, right knee cartilage is gone and has bone spurs (surgery slated late Jan), left knee will follow, Carpal tunnel release on right hand slated in Feb with left to follow, both feet and ankles full of spurs and nearly zero cartilage and COPD from burn pits in Afghanistan (during the MRI for my lungs, they pointed out my “bone windows” in my spine collapsing/degrading as a more severe issue, funny enough my spine doesn’t bother me! Lol) . I still work on hitting the gym to lift 5 times per week and doing whatever cardio I can around whatever painful part of my body is screaming that day.
All that said, I agree completely that staying moving and never taking a lot of time off really helps both physically and mentally.