Experts warn about bone risk from "female athlete triad"

Many female athletes are at a greater risk of bone stress injuries or fractures due to a condition they may never have heard of. It's called "female athlete triad," and according to new research, it's surprisingly common.

The term refers to a combination of three factors: low energy availability, menstrual irregularity, and low bone mineral density.

"Low energy availability can be thought of as not eating enough to replace the calories expended from exercise, either through a lack of nutritional knowledge or as a result of an eating disorder," lead study author and orthopaedic surgeon Dr. Elizabeth Matzkin told CBS News. "The decreased energy availability leads to menstrual irregularities, which then causes decreased bone mineral density that can ultimately result in osteopenia/osteoporosis." Osteopenia is when bone density is lower than normal but not low enough to be considered osteoporosis.

Since the 1972 passage Title IX of the Education Amendments Act -- a law prohibiting the exclusion of students from participating in sports based on gender -- female participation in sports has skyrocketed by over 900 percent in high schools and over 500 percent in colleges, according to the Women's Sports Foundation.

As more women and girls continue to play sports and compete, the study authors say it's imperative that they're aware of the risks of female athlete triad.

Both athletes and nonathletes participating in sports or any exercise can develop the syndrome. "The female athlete triad can be seen in women ranging from professional athletes to 'couch to 5k-er's' who are not training in a healthy manner," Matzkin noted.

But the study authors found that the likelihood of suffering a bone stress injury rises as the number of triad symptoms a woman has increases. The researchers found that having one of the three symptom was associated with a 15 to 21 percent increase in bone stress injuries; two symptoms, a 21 to 30 percent increase; and the presence of three symptoms with a 29 to 50 percent increase.

According to the study, female athletes diagnosed with poor nutrition or low energy availability are two to four times more likely to sustain a bone or joint injury. And those who self-reported abnormalities in their menstrual cycle were at a nearly three times greater risk of a sports-related injury.

Matzkin said that maximizing bone health at a young age is key to preserving it later in life.

"Younger females need to make sure that they are taking in adequate nutrients to replace the number of calories expended during exercise," she said. "They should also ensure they are receiving ample calcium and vitamin D either from eating a balanced diet or through supplements if dairy intake is not possible."

Bone density needs to be maximized by about the age of 25, Matzkin said. "Anything lost before then cannot be regained. Since females over the age of 25 have often reached maximal bone mineral density, they are now tasked with maintaining what they've accrued."

This can be done, she said, through good nutrition, energy balance, and exercise.

The authors of the study, published in the Journal of the American Academy of Orthopaedic Surgeons, concluded that any female athlete who falls under the "umbrella" of the triad should speak to their physicians to develop a plan and prevent future injuries.