Many teachers praise yoga as a smart way to fight degeneration of the hips and promote joint health.

But I kept hearing of women practitioners—including stars of the yoga circuit—who found themselves in urgent need of hip repairs. I followed the clues and put my findings in The New York Times. Here, I flesh out the story with new information, including how to reduce the danger.

I first became aware of the issue when I heard that Glenn Black, a prominent yoga teacher and body worker in the New York City region, had treated a famous yogi recovering from hip surgery. I interviewed Black, as The Science of Yoga recounts (pages 105 to 109).

After the book came out in February 2012, yoga insiders wrote to say it was not uncommon for hip troubles to strike leaders of the community and that a number of stars had undisclosed repairs. The claims were impossible to verify.

In late 2012, Michaelle Edwards, a popular yoga teacher in Hawaii, wrote to say that dozens of students she knew—mainly women—were suffering groin pain and hip injuries. Unlike sources who wanted anonymity, she said she was happy to speak out and, in the interest of preventing new injuries, go public with her information. We discussed the issue for months.

Edwards described how the elasticity of women became a liability when extreme bends resulted in chronic wear and tear on their hips. Over time, she said, the damage could develop into agonizing pain, and, in some cases, the need for hip repairs.

She sent me her book, YogAlign. It described her own hip pain long ago and how she eliminated it by developing a gentle style of yoga.

In July 2013, Edwards made her analysis public in elephant journal. She recommended that women whose hips felt tender when walking, or who experienced sharp pain when doing postures like the triangle, should consider easing up on their practice.

Despite the growing evidence, and Edward’s article, I was skeptical. After all, dozens of books and articles hailed yoga as great hip therapy. The titles include: Heal Your Hips, Easy Yoga for Arthritis, and Therapeutic Yoga for the Shoulders and Hips.

Finally, in late summer, when the news business slows, I made some calls.

To my astonishment, top surgeons declared the problem to be real—so real that hundreds of women yogis were coming to their offices in debilitating pain and undergoing costly operations to mend or replace their hips.

I spoke to surgeons in Atlanta, the Mayo Clinic, and the Hospital for Special Surgery in New York City, one of the world’s leading centers for orthopedic repair.

Bryan T. Kelly, a surgeon there, said yoga postures were well known for throwing hips into extremes of motion and rotation. “If that’s done without an understanding of the mechanical limitations of the joint, it can mean trouble,” he told me.

The same kind of damage, Dr. Kelly added, can strike dancers who push their legs to extremes, such as ballerinas. He said each year he operated on roughly fifty to seventy-five patients—mostly women—who danced or did yoga.

The surgeon at the Mayo Clinic, Michael J. Taunton, told me that a team of medical investigators in Switzerland had pinpointed the problem. They discovered that arthritis—the painful inflammation and stiffness of the joints usually associated with old age—could also strike the young.

The Swiss 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 FAI, in medical shorthand.

The name spoke to how the neck of the thigh bone (the femur) could swing so close to the hip socket (the acetabulum) that it repeatedly struck the socket’s protruding rim.

In 2008, the Swiss team published a lengthy study of FAI’s etiology, or cause. It noted that women between thirty and forty years of age whose activities made “high demands on motion” tended to show the hip damage more often. The paper specifically cited yoga.

On YouTube, I found animations (for instance, here, here, and here) that showed how leg motions could throw the femur’s neck into the socket’s rim. The visualizations made it easy to see how yoga could do likewise.

If you watch these animations, or look for similar ones on YouTube, note that the type of FAI that preferentially strikes women is known as “pincer,” alluding to how the hip bones can interact in the same way as the common tool. Pincer jaws come together like those of pliers.

The New York Times published my findings in the Sunday Review section in early November 2013 under the headline “Women’s Flexibility Is a Liability (in Yoga).”

The article quoted Edwards as warning practitioners to be cautious when doing seated forward bends (like Paschimottanasana), standing forward bends (like Uttanasana) and forward lunges (like Anjaneyasana)—moves that when done forcefully can push the neck of the femur into the socket’s rim.

My article noted that yoga was just one of many culprits. Medical experts pointed to such contributing factors as bone misalignments, excess body weight and subtle deformities of the hip joint that differ from person to person. It said the variations make it hard to predict who was most at risk.

The story also observed that yoga probably does help many people who suffer from arthritis, which can strike not just the hips, but fingers, knees and shoulders. It apparently does so by fighting inflammation.

Gentle yoga probably helps the hips, too, but, as Dr. Taunton of the Mayo Clinic observed, the bending can become “too much of a good thing.”

For days, the story topped the paper’s most-emailed list. Along with denunciations, I received lots of positive feedback, including from yogis who had suffered hip damage and replacements. “Thanks so much,” wrote a yoga celebrity, calling the article balanced and “very helpful.”

A physical therapist in Los Angeles wrote to propose a contributing factor hidden in the hip’s welter of muscles, tendons and ligaments.

She suggested that, over years of practice, an individual who followed yoga’s emphasis on forward bends could develop joint imbalances in which the hip’s rear area became flexible even as the front remained relatively tight. The result, she said, was that some poses could readily pull the femoral head forward, causing impingement.

“Many of these women can be helped,” she wrote. “If evaluated properly and given the tools and knowledge regarding what is causing their pain, what imbalances they have and how to work on correcting them, they can use yoga to correct the problem.”

My science guru, Mel Robin, sent a note full of good information. Mel is an Iyengar teacher and a chemical physicist who worked for decades at Bell Labs when it excelled at innovation. I studied yoga with him in Pennsylvania and, in The Science of Yoga (pages 91 to 95), spoke of his illuminating classes.

In his note, Mel said that his Handbook for Yogasana Teachers, published in 2008, discussed a number of postures than can throw the hip bones into conflict (pages 341 to 345). He called it bone-on-bone contact.

The book explained how subtle body adjustments can avert the strikes, giving particular attention to Trikonasana (the triangle pose) and Anantasana (the side-reclining leg lift). In his note, Mel called bone conflicts “largely an unrecognized aspect of our practice” and said the problem can be avoided “if we practice in a more mindful way.”

Edwards, the Hawaiian yoga teacher who helped me understand the problem, said she had been besieged by reporters and people around the globe with hip troubles. In a follow-up piece for Elephant Journal, she faulted yogis who, when facing the topic of injury, run in the opposite direction. “It may be time to get informed, not defensive,” she wrote. “Broad is on our team.”

From my own practice and research, I know that yoga can heal, calm, renew, strengthen, lift moods, lower the risk of heart disease, increase flexibility and balance, counter aging and improve sex and intimacy.

Hip awareness can only reduce yoga’s risks and help us better enjoy its many benefits. I wrote this account in that spirit. I’m grateful to all who helped me understand the issues and hope the information helps you improve your own practice.

Onward to better yoga!

Relephant Reads:

> 3 Common Yoga Injuries & How to Avoid Them.

> Yoga Injuries: Waves of Compassion.

> 3 Tips to Prevent Common Yoga Injuries.