Can Exercise Prevent Knee Osteoarthritis?

New research in the November Issue of Journal of the American Medical Association says that knee osteoarthritis has doubled since the mid-20th century. A study of human skeletons housed in the vaults of US museums is providing new perspective on the current thought that knee osteoarthritis is caused by aging and being overweight.
 
Researchers at Harvard University found that increased prevalence of knee issues was over 2 times higher for people who died between 1976 and 2015 than for those who died between 1905 and 1940 even after they took out age and body mass index factors. “At a given age, if you were born after World War II you are more than twice as likely to have osteoarthritis in your knee than if you had been born earlier, regardless of your weight,” said study coauthor Daniel Lieberman, PhD.
 
The missing link? Although knee osteo may be caused by several issues (including an inflammatory diet, walking/running on hard pavement, and inappropriate footwear), the shift toward a more sedentary lifestyle is now being blamed as a big factor. Exercise strengthens muscles to appropriately distribute loads across the joints and also increases bone density/bone health. And “weight-bearing exercise forces the nutrients in the joint fluid to diffuse into knee cartilage, and that is its main source of nutrition because knee cartilage in adults has no blood supply other than that promoted by physical activity.”
 
Interesting to note that the researchers documented cases of knee osteoarthritis in 2000 skeletal remains of people who died between 1905 and 2015, and 176 skeletons from prehistoric hunter-gatherers and early farmers who lived between 6000 to 300 BP (before present). All were at least 50 years old when they died. Research confirmed that it’s an ancient ailment: 8% of prehistoric skeletons had knee osteo (whereas 16% of postindustrial skeletons had it).
 
(Study: http://www.pnas.org/content/114/35/9332, article by Jennifer Abbasi, Published November 22, 2017. doi:10.1001/jama.2017.16144
https://jamanetwork.com/journals/jama/fullarticle/2664339 )

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