Weak in the Knees: Osteoarthritis Doubles Among 21st Century Americans


Knee osteoarthritis (OA) is the most common and debilitating joint condition in the United States, affecting more than 19% of adults over age 45. That statistic is not only high, but it is alarming when considering it has more than doubled since the mid-20th Century. Scientists have attempted to explain the increase in OA by citing increased longevity and a higher incidence of obesity, in essence blaming wear and tear on knee degeneration. However, new research flies in the face of the wear and tear theory, and offers new insights into the increased incidence of knee OA.

New Study Demolishes Wear and Tear Theory

In 2017, a research team led by Ian J. Wallace wanted to know if wear and tear was the primary cause of degenerative knee osteoarthritis. They reasoned that humans of the past were move physically active than today’s sedentary Americans, and therefore the knees of past generations should show signs of greater wear and tear due to greater stresses placed on the knees over the course of a lifetime.

The research team looked at the knees of cadavers over age 50, scanning prehistoric times to the present, with the oldest knees dating back around 6000 years. OA was diagnosed based on the presence of eburnation, the polishing evident from bone-on-bone contact seen in OA.

The study samples (n = 2,576) included:

  • Early industrial individuals over age 50 (n = 1,581) who were inhabitants of Cleveland, Ohio and St. Louis, Missouri and who died between 1905 and 1940
  • Postindustrial individuals (n = 819) who lived in Albuquerque, New Mexico and Knoxville, Tennessee, who died between 1976 and 2015.
  • Prehistoric individuals whose samples included skeletons from archeological sites in Alaska, California, New Mexico, Kentucky, and Ohio, estimated to be over age 50, who were hunter-gatherers (n = 116) and early farmers (n = 60).

Study Findings

After data analysis, the research team found that:

  • Knee OA was higher among individuals from the postindustrial era compared with individuals from early industrial and prehistoric times
  • Females were more affected than males
  • After controlling for sex, postindustrial knee OA prevalence was 16%, 2.6 times higher that the early industrial sample (6%) and 2 times higher than the prehistoric sample (8%)
  • Among postindustrial individuals with knee OA, 42% had OA in both knees, 2.5 times higher than the prehistoric sample (17%) and 1.4 times higher than the early industrial sample (30%)

Study Conclusions

Researchers concluded that neither longevity nor body weight explain the dramatic increase in the incidence of knee OA in post-industrial age Americans. They suggest that rather than wear and tear, physical inactivity may be the culprit behind increased knee OA. Sedentary lifestyles among both children adults, long hours of sitting and altered loading patterns may lead to structural weakness of knee cartilage. They add that chronic inflammation, diets high in refined carbohydrates and adiposity may also contribute to OA.

How OA Affects Gait

OA in your knees can alter your gait as you compensate to avoid pain. Over time, altered gait can lead to muscle imbalances and strain that lead to even more pain, complicating matters. The sports medicine team at NYDNRehab knows how debilitating OA knee pain can be.

Apos therapy, a treatment that retrains the knee muscles to restore proper alignment and gait, has been shown to be successful in treating pain and improving movement in patients with OA. If you live in NYC, you do plenty of walking. Don’t let pain from knee OA keep you from getting where you need to go. Contact NYDNRehab today, and see why our knee pain specialists are the very best in NYC.


Wallace, IJ et al. (2017). Knee osteoarthritis has doubled in prevalence since the mid-20th century. PNAS; published ahead of print August 14, 2017, doi:10.1073/pnas.1703856114


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