Why do so many middle-aged women develop osteoarthritis? Scientists believe that declining estrogen levels may play a role.
Osteoarthritis is often called a wear-and-tear disease because it develops in joints after many years of use. Aging increases the risk of developing osteoarthritis, but it's not the sole cause. Scientists aren't sure exactly what causes the condition, but several factors play a role in its development. These include genetic predisposition, obesity, prior joint injuries, wear and tear on the joints due to repeated overuse or sports-related activities, muscle weakness, and nerve injury.
Now a study reported in the journal Arthritis and Rheumatism (Volume 54, page 2481) suggests that low estrogen levels are linked to osteoarthritis of the knee in middle-aged women.
Following up on findings from animal studies, researchers from the University of Michigan measured the estrogen levels of more than 800 premenopausal and perimenopausal women. Based on these results, they ranked the study participants into three groups according to their estrogen levels. The women had yearly x-rays of both knees and answered questions about knee pain, their general health, and various lifestyle factors.
After taking into account osteoarthritis risk factors such as body mass index, the researchers found that women with the lowest estrogen levels were nearly twice as likely to develop osteoarthritis over the next three years as were those with higher levels.
These findings may help explain why signs of osteoarthritis tend to appear when women are in their 40s, a time of fluctuating or declining estrogen levels. The relationship between estrogen and osteoarthritis isn’t clear. However, the hormone is believed to interfere with arachidonic acid, a substance in the body that is associated with pain and inflammation. The researchers suggest that a better understanding of estrogen’s apparent protective effect on the knee may lead to new approaches to osteoarthritis management.
