Osteoarthritis is not an equal-opportunity disorder: It appears to favor women. Among people with osteoarthritis, there are twice as many women as men, especially for those with arthritis in the knees and hands. Symptoms typically begin to appear in women in their 40’s and 50’s, and the disparity becomes even greater after age 55, after women enter menopause.
What could account for these differences? There could be a number of reasons for this disparity.
By far the most important risk factor for osteoarthritis in women, as in men, is obesity. Women who go through menopause often gain weight, and the increased stress on the joints may explain the rise in osteoarthritis seen among women after age 55. By the time a woman reaches 65, she is twice as likely as a man to experience osteoarthritis symptoms.
Another possible explanation is anatomical: women’s hips are wider than men’s. The angle formed by the hip bones being wider than the knees puts more stress on the outside of the knees. This “knock-kneed” position, even if slight, can cause osteoarthritis over time in some women.
Women are also more likely to develop a condition called patellofemoral syndrome, in which the kneecap (patella) does not glide smoothly over the joint and rubs against the lower part of the thighbone (femur). This misalignment may be exacerbated by hyperextended knees in women who wear high heels. The recurrent rubbing of the kneecap on the thighbone causes wear and tear that can progress to arthritis and cause pain in the front of the knee.
The increased prevalence of osteoarthritis in women has also triggered studies to determine the role of hormones. While the roles of hormones such as estrogen and progesterone in osteoarthritis are unclear, research has shown that hormone replacement therapy (HRT) may have a protective effect. The 1997 Chingford Study in London, for example, found that among more than 1,000 women, those who used HRT experienced less osteoarthritis of the knee (as seen on x-rays) and slightly less in the hands. Research exploring the influence of hormones on osteoarthritis is continuing.
Other investigators have studied the role of a hormone called relaxin, which is increased during pregnancy and makes joints more lax, causing potential instability. Elevated relaxin has been proposed as a possible explanation for the increased prevalence of osteoarthritis of the hands seen in women compared with men. Studies are continuing to analyze this relationship.
Another theory relates to sports injuries. The increase in girls participating in high school and college sports over the last couple of decades means more females are experiencing sports injuries, particularly tears to the anterior cruciate ligament (ACL) of the knee. This injury on its own places an individual at an increased risk of osteoarthritis, even if it is surgically repaired. Any instability in the knee generates wear and tear over time.
We could actually see an increase in osteoarthritis in women in the coming years as girls with ACL injuries grow up. One study found that among female soccer players who had sustained ACL injuries, more than half developed x-ray signs of osteoarthritis in the following 12 years.
Women of all ages should take precautions on how to reduce the risk of developing osteoarthritis and to manage it well if you already have it, including:
Medical Director, Women's Sports Medicine Center, Hospital for Special Surgery
Assistant Attending Physician, Hospital for Special Surgery
Assistant Professor of Medicine, Weill Cornell Medical College