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Knee osteoarthritis has doubled in prevalence since the mid-20th century

PainSci » bibliography » Wallace et al 2017
Tags: knee, arthritis, inflam-sys, neat, counter-intuitive, history, leg, limbs, pain problems, aging

Two articles on PainSci cite Wallace 2017: 1. The Complete Guide to Chronic Tension Headaches2. Your Back Is Not Out of Alignment

PainSci commentary on Wallace 2017: ?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

Knee osteoarthritis is thought of a “wear-and-tear” problem aggravated by weight and age. In this experiment, this assumption was tested for the first time using “long-term historical or evolutionary data.” They looked at the skeletal remains of older people with a well-documented body mass index from the last two centuries (industrial and post-industrial); they also looked at prehistoric knees. The prevalence of osteoarthritis has roughly doubled in recent history (20th century) — and that number didn’t change when weight and age were factored out. The implications are clear: loading and longer lifespans are almost certainly not the cause of knee arthritis!

So what, then? Although this data doesn’t show it, the unconfirmed but obvious candidate is the surge in the modern lifestyle diseases: metabolic syndrome, diabetes, heart disease (see Kluzek et al or Jiang to start down that rabbit hole). Which is good news: those problems are more preventable than aging.

~ Paul Ingraham

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

Knee osteoarthritis (OA) is believed to be highly prevalent today because of recent increases in life expectancy and body mass index (BMI), but this assumption has not been tested using long-term historical or evolutionary data. We analyzed long-term trends in knee OA prevalence in the United States using cadaver-derived skeletons of people aged ≥50 y whose BMI at death was documented and who lived during the early industrial era (1800s to early 1900s; n = 1,581) and the modern postindustrial era (late 1900s to early 2000s; n = 819). Knee OA among individuals estimated to be ≥50 y old was also assessed in archeologically derived skeletons of prehistoric hunter-gatherers and early farmers (6000-300 B.P.; n = 176). OA was diagnosed based on the presence of eburnation (polish from bone-on-bone contact). Overall, knee OA prevalence was found to be 16% among the postindustrial sample but only 6% and 8% among the early industrial and prehistoric samples, respectively. After controlling for age, BMI, and other variables, knee OA prevalence was 2.1-fold higher (95% confidence interval, 1.5-3.1) in the postindustrial sample than in the early industrial sample. Our results indicate that increases in longevity and BMI are insufficient to explain the approximate doubling of knee OA prevalence that has occurred in the United States since the mid-20th century. Knee OA is thus more preventable than is commonly assumed, but prevention will require research on additional independent risk factors that either arose or have become amplified in the postindustrial era.

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