Girls are up to 10 times more likely than boys to suffer knee injuries in sports like soccer and basketball. Researchers in Akron have discovered that genetic differences help explain the disparity.
But in this week’s Exploradio, WKSU’s Jeff St.Clair reports that lack of proper sports training is also partly to blame.
Two teams of 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.
Jewell recalls a similar game about a year and a half ago when her knee gave out, "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. She says, at a big soccer tournament, "I will see a couple with the same brace as me.”
An epidemic of knee injuries in female athletes
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.
Jones describes the technique of attaching the new tendon 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.
He says the majority of kids that come into his office with a variety of sports related knee injuries like ACL tears, 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.
Testing the tissues for genetic differences
Dr. Jones 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.
The result, he says, “was a bit of a surprise.”
Landis says three genes that build and maintain ligaments are different for girls and boys. And that makes the ACL's tissue structurally different which Landis says, "may provide a propensity to injury under the same types of stresses.”
The results are a concern for Dr. Jones in treating young athletes. He believes that it’s inherent in women that their ACL’s are structurally weaker, and additionally, that the way girls use their bodies in sports, "really predisposes them to tear their ACL.”
ACL tears in girls is multifactorial problem
Timothy Hewitt is head of the Sports Health and Performance Institute at Ohio State University.
He says without doubt the rash of knee injuries in female athletes is, "a multifactorial 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.
Hewitt describes the hip and knee diving in toward the midline of the body as a girl lands. He says this happens with the knee relatively straight and, "most if not all of the weight is on a single, very flat foot." The motion puts most of their weight on a single leg, and a lot of strain on the knee ligaments.
Hewitt says this is because girls are engaging different muscle groups than boys, mainly the quadriceps instead of the hamstring and glutes.
Training for girls, and their coaches is needed
But, while genes can’t be changed, Hewitt says girls can be trained to use their muscles more efficiently in better techniques for landing and turning.
And he says that’s the good news, "because those are the only factors that are actually modifiable... 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.
Hewitt says training to prevent sports injuries in girls has been sadly underutilized. He's passionate about reversing this deficit. Hewitt says, "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.
