https://www.health.harvard.edu/blog/the-mysterious-rise-in-knee-osteoarthritis-2017100212504
Osteoarthritis is the form of joint disease that’s often called “wear-and-tear” or “age-related,” although it’s more complicated than that. While it tends to affect older adults, it is not a matter of “wearing out” your joints the way tires on your car wear out over time. Your genes, your weight, and other factors contribute to the development of osteoarthritis. Since genes don’t change quickly across populations, the rise in prevalence of osteoarthritis in recent generations suggests an environmental factor, such as activity, diet, or weight.
Osteoarthritis of the knee will affect at least half of people in their lifetime, and is the main reason more than 700,000 people need knee replacements each year in the US.
To explain the rise in the prevalence of osteoarthritis in recent decades, most experts proposed that it was due to people living longer and the “epidemic of obesity,” since excess weight is a known risk factor for osteoarthritis. Studies have shown not only that the risk of joint disease rises with weight, but also that even modest weight loss can lessen joint symptoms and in some cases allow a person to avoid surgery.
But a remarkable new study suggests there is more to the story.
The findings were intriguing:
- The prehistoric skeletons and early 1900s cadavers had similar rates of knee osteoarthritis: 6% for the former and 8% for the latter.
- With a prevalence of 16%, the more recent skeletons had at least double the rate of knee osteoarthritis as those living in centuries past.
- Even after accounting for age, BMI, and other relevant information, those in the post-industrial group had more than twice the rate of knee osteoarthritis as those in the early industrial group.