Even when it comes to osteoarthritis, men and women differ. And those gender differences matter because better, more timely treatments may come with understanding how men and women develop OA and why.

“Men and women may need interventions that are different. And earlier recognition of issues may be needed more for one gender than another,”  says Barbara A. Rakel, PhD, associate professor in the College of Nursing at the University of Iowa in Iowa City.

In Rakel’s 2011 study of men and women with knee osteoarthritis, for example, women had more pain than men but took similar amounts of medication. “Although we treat men and women similarly,” says Rakel, “that women have more pain should probably drive treatment that’s different than for men.”

Still, gender differences are not easy to tease apart, nor are they entirely understood. Below, researchers describe what they know.

Women Get the Lion’s Share

According to the Centers for Disease Control and Prevention, men have a 45 percent lower risk of knee OA and a 36 percent lower risk of hip OA than women.

“Women have the higher burden of disease,” agrees Mary I. O’Connor, MD, chair of the Department of Orthopaedic Surgery at the Mayo Clinic in Jacksonville, Fla. “We [women] are much more likely to get knee osteoarthritis, for example, particularly after menopause when our risk goes way up.” 

According to a 2010 study review at the University of California, that’s true of hip and hand OA as well. 

Estrogen’s Role

Although cartilage contains estrogen receptors (molecules that respond to estrogen), no data definitively links increased osteoarthritis in women to hormones, says Dr. O’Connor.  Still, some studies have found a possible association including a 2006 University of Michigan study, which found that women with knee OA are likely to have low levels of estrogen.

Studies looking at the effect of hormone replacement (HRT) are equivocal. For instance, a 2006 study at the University of Iowa that examined data involving 26,000 women from the Women’s Health Initiative found that women taking estrogen had significantly lower rates of hip replacement but not knee replacement.

“Women on hormone replacement therapy might be less likely to lose cartilage over time”— as evidenced on x-rays — “and less likely to get hip OA or hip replacements,” says rheumatologist/epidemiologist  and review author Joanne M. Jordan, MD, MPH, director of the Thurston Arthritis Research Center at the University of North Carolina in Chapel Hill. “Yet in another study that looked at HRT for preventing knee pain” — a 1996 multi-institutional study including the University of California-San Francisco and others  — “it didn’t appear effective.”