The researchers at Harvard scoured across the United States for skeletons in a quest to further understand osteoarthritis. Ian Wallace, a postdoctoral fellow in palaeoanthropology and lead author of the study, together with his team analysed more than 2,000 skeletons—ranging from ancient remains found by archaeologists to bodies unclaimed from morgues to cadavers at medical schools. They were particularly interested in the polished surfaces of the joints, called eburnation, which were caused by cartilage breaking down and bones rubbing against each other.

After which, the study reported the findings in a newly published journal in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Double the risk in modern times

Osteoarthritis affects one in five Americans over the age of 45. The last 50 years has also seen the rise of osteoarthritis to have doubled since World War II. The disease is thought to be the inevitable fate of old age and increased body mass index. However, this study has dispelled the thinking—further suggesting that there are other factors at play.

The skeletons were divided into pre-industrial, early industrial, and post-industrial periods. The wear-and-tear of each skeleton was analysed, noting the age and body mass index of the cadavers, where possible. A mathematical control was applied and in conclusion, 18% of the skeletons from the recent post-industrial periods had signs of osteoarthritis compared to just 6% and 8% from the earlier pre-industrial and early industrial periods.

This showed that neither age nor weight were to blame for the cause of the osteoarthritis. What’s worth noting was arthritis was also seen in Egyptian mummies and Neanderthals. This also meant that arthritis was preventable, provided there was a further understanding of what it was that our ancestors did, that made them less likely to suffer from the condition.

Move more, not less

Age and obesity are still clear players in the rise of osteoarthritis. People have longer life spans in modern times—with the process of ageing naturally breaking down connective tissue, while increased weight also puts strain on the joints that will eventually be damaged. Although the researchers have a good theory of the other player which contributes to the cause, more research is implored.

Harvard professor Daniel Lieberman and senior author of the paper hypothesised that physical inactivity may be the culprit. “It is one of the biggest differences between people who live today and people who lived in the past whose risk of arthritis was much lower—like many of our grandparents, who tended to sit much less and walk much more than we do,” elaborated Lieberman.

"The most important message here is that we shouldn't consider arthritis a wear-and-tear disease of age," he continued. "Arthritis is a disease that becomes more common as you age; but it's not caused by 'wear-and-tear'. If anything, it might be caused by the absence of physical activity. So, a major way to prevent arthritis could be moving more, not less,” remarked Lieberman.

Professor David Felson from Boston University Medical School and the paper’s co-author stated that exercise makes the joints more strain-resistant and that “the cartilage gets thicker and the muscles that support and protect the joints get stronger. And joints are hardier when you're active. So, the absence of activity isn't necessarily good for our joints,” he opined.

Lieberman continued, “knee osteoarthritis is not a necessary consequence of old age. We should think of this as a partly preventable disease. Wouldn’t it be great if people could live to be 60, 70, or 80 and never get knee osteoarthritis in the first place? Right now, our society is barely focusing on prevention in any way, shape, or form. So, we need to redirect more interest towards preventing this and other so-called diseases of ageing.” MIMS

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