Osteoarthritis (OA) is the wear-and-tear kind. A recent study discussed in JAMA looked at skeletal remains and found that even after controlling for weight and age, if you were born in a developed country after WWII, you're more than twice as likely to have OA of the knee.
That is to say: a two hundred pound man born in 1945 and who died at 70 is twice as likely to have OA of the knee than a two hundred pound man born in 1900 and who died at 70.
What changed since WWII? Wealth plus automation = less exercise. This is quite consistent with the work done already showing that runners are slightly LESS likely to have knee problems than non-runners. (This should shut up those annoying people telling you you're going to mess up your knees.) As the JAMA editorial states, it's also consistent with evolutionary medicine - that if we behave as evolution designed us to behave - i.e., running around all the time doing stuff and not sitting at home in front of glowing screens - that we're more likely to be healthy.
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