Knee Osteoarthritis has Doubled in Prevalence Since the Mid-20th Century

Did you know that Knee Osteoarthritis (OA) has doubled in prevalence since the mid-20th century? At Restore Osteo of Colorado, we take knee pain seriously. We offer a variety of treatment options such as bracing, physical therapy, joint injections, and lots more. Our specialists can work with you to create an individualized treatment plan to improve your knee function, relieve pain, and potentially avoid knee replacement surgery. If you are experiencing symptoms of Knee OA, we can help you with that.

Check out this study below from PubMed that outlines how OA, a disabling joint disease, has doubled in prevalence since the mid-20th century.


Knee osteoarthritis is a highly prevalent, disabling joint disease with causes that remain poorly understood but are commonly attributed to aging and obesity. To gain insight into the etiology of knee osteoarthritis, this study traces long-term trends in the disease in the United States using large skeletal samples spanning from prehistoric times to the present. We show that knee osteoarthritis long existed at low frequencies, but since the mid-20th century, the disease has doubled in prevalence. Our analyses contradict the view that the recent surge in knee osteoarthritis occurred simply because people live longer and are more commonly obese. Instead, our results highlight the need to study additional, likely preventable risk factors that have become ubiquitous within the last half-century.

Keywords: arthritis, aging, obesity, mismatch disease, evolutionary medicine

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.

Osteoarthritis (OA) is the most prevalent joint disease and a leading source of chronic pain and disability in the United States (1) and other developed nations (2). Knee OA accounts for more than 80% of the disease’s total burden (2) and affects at least 19% of American adults aged 45 y and older (3). Substantial evidence indicates that knee OA is proximately caused by the breakdown of joint tissues from mechanical loading (4) and inflammation (5), but the deeper underlying causes of knee OA’s high prevalence remain unclear and poorly tested, hindering efforts to prevent and treat the disease. Two recent public health trends, however, are commonly assumed to be dominant factors (67). First, because knee OA’s prevalence increases with age (8), the rise in life expectancy in the United States since the early 20th century is thought to have led to high knee OA levels among the elderly, with the presumption that, as people age, their senescing joint tissues accumulate more wear and tear from loading (9). Second, high body mass index (BMI) has become epidemic in the United States in recent decades and is a well-known risk factor for knee OA (8), probably because of the combined effects of joint overloading and adiposity-induced inflammation (10). Whether increases in longevity and BMI are responsible for current knee OA levels has never been tested, but this assumption has led many to view the disease’s high prevalence as effectively unpreventable, since aging is untreatable, and the high BMI epidemic is intractable (811).

One underused yet potentially powerful way to identify and assess the risk factors responsible for current knee OA levels is to examine long-term changes in the disease’s prevalence by comparing contemporary with historic and prehistoric populations (12). Epidemiological studies of present day populations are valuable but are limited in their ability to analyze risk factors that are now pervasive but used to be less common. It is difficult to find large samples of living Americans whose lifestyles, including physical activity levels and diet, resemble those of past generations. Although many variables cannot be measured and thus controlled in epidemiological studies of people living in the past, a major benefit of analyzing populations over historical and evolutionary time is to assess known risk factors under different environmental conditions and thus bring to light the effects of risk factors that might not be apparent or testable in modern populations alone. Furthermore, although knee OA is known to be ancient (12), we know very little about changes in its prevalence over time. Low levels of knee OA have been reported for some historic and prehistoric populations (1317), suggesting that the disease’s prevalence has recently increased, but these studies used different diagnostic criteria than those used to diagnose knee OA in living patients, used samples composed mostly of younger individuals, and did not account for BMI, complicating comparisons with modern epidemiological data.

Here, we investigate long-term trends in knee OA prevalence in the United States and evaluate the effects of longevity and BMI on levels of the disease by comparing the prevalence of knee OA among people who lived during the early industrial era (19th to early 20th centuries) with that of people from the modern postindustrial era (late 20th to early 21st centuries). We studied knee OA in the largest available collections of cadaver-derived skeletal remains of people of documented age, BMI, sex, and ethnicity. To further consider knee OA levels from an evolutionary perspective, we also analyzed knee OA in a large sample of archeological skeletons of prehistoric Native American hunter-gatherers (6000–300 B.P.) and early farmers (900–300 B.P.). Although BMI is undocumented for prehistoric skeletons, the age at death and sex can be estimated, allowing us to assess the prevalence of knee OA among older individuals in these populations. The skeletal collections used in this study are, by necessity, samples composed of individuals who could not be randomly selected and for whom we lack comprehensive demographic and contextual information. Despite these limitations, these samples constitute the best available evidence for knee OA levels in the United States during earlier time periods to test if prevalence of the disease is higher today than in the past...

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