Women’s Flexibility Is a Liability (in Yoga)

Even so, last year, after my book on yoga came out, letters from injured guys prompted me to see if the practice, despite its benefits, was hurting one sex more than another. To my surprise, reports from hospital emergency rooms showed that, proportionally, men got injured more often than women and suffered damage that was far worse, including fractures, dislocations and shattered backs.

It made sense. Women are well known to be more flexible than men. Macho guys, yoga teachers told me, too often used their muscles to force themselves into challenging poses and got hurt. The overall numbers were relatively small but large enough to argue that men who did yoga should exercise caution.

Earlier this year, the picture of female superiority began to blur when a prominent yoga teacher in Hawaii wrote me about a poorly known threat to women.

The teacher, Michaelle Edwards, said that women’s elasticity became a liability when extreme bends resulted in serious wear and tear on their hips. Over time, she said, the chronic stress could develop into agonizing pain and, in some cases, the need for urgent hip repairs. Ms. Edwards sent me her book, “YogAlign.” It described her own hip pain long ago and how she solved it by developing a gentle style of yoga.

Her warning contradicted many books, articles and videos that hailed yoga’s bending and stretching as a smart way to fight arthritic degeneration.

I put her cautions aside. Finally, in late summer, I got around to making some calls.

To my astonishment, some of the nation’s top surgeons declared the trouble to be real — so real that hundreds of women who did yoga were showing up in their offices with unbearable pain and undergoing costly operations to mend or even replace their hips.

“It’s a relatively high incidence of injury,” Jon Hyman, an orthopedic surgeon in Atlanta, told me. “People don’t come in often saying I was doing Zumba or tai chi” when they experienced serious hip pain, he said. “But yoga is common.”

Dr. Hyman said his typical yoga patient was a middle-aged woman, adding that he saw up to 10 a month — or roughly 100 a year. “People need to be aware,” he said. “If they’re doing things like yoga and have pain in the hips, they shouldn’t blow it off.”

Bryan T. Kelly, an orthopedic surgeon at the Hospital for Special Surgery in Manhattan, echoed the warning, saying yoga postures were well known for throwing hips into extremes. “If that’s done without an understanding of the mechanical limitations of the joint, it can mean trouble,” he said in an interview.

The same kind of damage, Dr. Kelly added, can strike dancers who overdo leg motions. Each year, he said, roughly 50 to 75 of his patients who danced or did yoga underwent operations. Most, he noted, were women.

Curious about the back story, I found that medical detectives in Switzerland had pinpointed the origin of the hip trouble more than a decade ago. Arthritis is usually associated with old age, but they discovered it can also strike the young and active.

Women’s hips showed particular vulnerability. By nature, their pelvic regions support an unusually wide range of joint play that can increase not only their proficiency in yoga but, it turned out, their health risks. The investigators found that extreme leg motions could cause the hip bones to repeatedly strike each other, leading over time to damaged cartilage, inflammation, pain and crippling arthritis. They called it Femoroacetabular Impingement — or F.A.I., in medical shorthand. The name spoke to a recurrence in which the neck of the thigh bone (the femur) swung so close to the hip socket (the acetabulum) that it repeatedly struck the socket’s protruding rim.

The main investigator was Reinhold Ganz, an orthopedic surgeon at the University of Berne, in Switzerland. Between 2001 and 2008, his team published many studies, the 2008 one noting that women between 30 and 40 years of age whose activities made “high demands on motion” tended to show the hip damage more often. The paper specifically cited yoga.

The discovery resonated. I found that hundreds of orthopedic surgeons in the Mediterranean region heard a conference presentation in 2010 that linked F.A.I. to middle-aged women who do yoga.

Michael J. Taunton, an orthopedic surgeon at the Mayo Clinic, told me that he first learned of the danger a half decade ago and now annually performs 10 to 15 hip replacements on people who do yoga. About 90 percent, he added, are women.

Stuart B. Kahn, a rehabilitation doctor at the Beth Israel Medical Center in Manhattan, called F.A.I. “an emerging topic as we learn more about what causes hip pain and osteoarthritis.” He said much remains unknown.

Hip damage, for instance, can have complex causes. In addition to yoga, contributing factors can include bone misalignments, excess body weight and subtle joint deformities that differ from person to person. Hip scientists are exploring such factors, but the variations make it hard to predict who is most likely at risk.

Another complication is that yoga probably does help millions of people cope with arthritis, which can strike not just the hips but fingers, knees and shoulders. Scientists have long reported that yoga’s movements can help fight joint inflammation.

Gentle yoga probably helps the hips, too. But, as Dr. Taunton put it, the bending can become “too much of a good thing.”

Ms. Edwards, the yoga teacher in Hawaii, said she warns practitioners to be cautious if doing seated forward bends (like Paschimottanasana), standing forward bends (like Uttanasana) and forward lunges (like Anjaneyasana) — moves that can force the neck of the femur into the socket’s rim.

Recently, she aired her warnings in Elephant Journal, an online yoga magazine. If a woman feels hip tenderness when walking, or sharp pain when doing poses like the revolved triangle, Ms. Edwards said, “you may want to back off.”

Surgeons agree that women who moderate their practice can probably avoid hip trouble.

Unfortunately, yoga teachers too often encourage students to “push through the pain.” That’s not smart. Pain is nature’s warning system. It’s telling you that something has gone awry.

Better to do yoga in moderation and listen carefully to your body. That temple, after all, is your best teacher.