Girls are up to 10 times more likely than boys to suffer knee injuries in sports like soccer and basketball.
Researchers at Children's Hospital in Akron have discovered that genetic differences help explain the disparity. A lack of proper sports training is also partly to blame. Jeff St. Clair of member station WKSU in Kent reports.
Teenage girls scramble in a hard fought match in the sprawling soccer complex next to the expressway interchange near Lodi. Fifteen year-old Bethany Jewell is from Salem and plays on the Keystone traveling team. A sturdy metal brace grips her right knee as she runs down the field. She recalls a similar game about a year and a half ago…
“And it just gave out on me all of a sudden out of nowhere. Nobody was even near me. I just fell and I knew it had happened again.”
Bethany knew the feeling because she had torn her other knee at the age of 12. Her love of soccer keeps her in the game. She says it’s not uncommon to see other girls sporting protective gear.
“I’ll go to a big soccer tournament and I will see a couple with the same brace as me.”
Kerwyn Jones at Akron Children’s Hospital performed both of Jewell’s knee surgeries. He rebuilt her right ACL, her anterior cruciate ligament, using one of her hamstring tendons.
“What we used on Bethany was, on the top we suspended it with a tiny metal clip, and we call it a button because it’s just like a button on your shirt.”
As an orthopedic surgeon Jones says he sees a lot of knee injuries in young girls.
“The majority of the kids that come into my office, and it’s not just ACL tears, a lot of the problems around the knee - knee cap dislocations, sprains of the ligaments - it’s predominantly the girls that are coming into the office and not the boys.”
In fact girls playing soccer and basketball and other sports are two to 10 times more likely than boys to tear their ACL’s. That got Jones wondering what differences in the ligaments themselves could be causing this disparity.
He saved samples of torn ligaments from 14 girls and boys who underwent ACL surgery, froze them and sent them to William Landis, an expert in bones and cartilage at the University of Akron.
Landis says microarray analyses, tests that show what genes are most active in the ligament cells, revealed stark differences in the sexes.
“For us it was a bit of a surprise.”
Landis says three genes that build and maintain ligaments are different for girls and boys.
“They’re just structurally different which may provide a propensity to injury under the same types of stresses.”
The results are a concern for Dr. Jones in treating young athletes.
“It’s inherent in women that their ACL’s are structurally weaker and add to that, that they are responding and reacting differently in sports, that really predisposes them to tear their ACL.”
Timothy Hewitt is head of the Sports Health and Performance Institute at Ohio State University.
“This is no doubt a multifactoral problem.”
In addition to genetics, other factors are anatomy and physics. He says the way many girls stop and turn puts intense pressure on their knees.
“The hip and knee are diving in toward the midline of the body. This happens with the knee relatively straight when they land. Most if not all of the weight is on a single, very flat foot - the individual lands flat-footed with most of their weight on a single leg.”
Hewitt says this is because girls are engaging different muscle groups than boys. But, while genes can’t be changed, he says girls can be trained to use their muscles more efficiently in better techniques for landing and turning.
“And that’s the good news in all this because those are the only factors that are actually modifiable that we can change with training.”
Hewitt believes the epidemic of ACL tears in girls is preventable. He’s seen training reduce the risk of injury by one-half to two-thirds, but it’s not being widely used.
“It has been underutilized. People have been undereducated. We have to get this out to the schools, to the athletic directors, to the coaches...”
Hewitt says training girls to prevent knee injuries also makes them better balanced, and better athletes.
The findings of the genetic underpinnings of ACL tears in girls was presented at the annual meeting of the American Academy of Orthopaedic Surgeons.