It’s been known for years that female athletes have a much higher risk for painful, season-ending injuries to their anterior cruciate ligament (or ACLs) than their male counterparts.
But new research conducted in Akron is showing clues to why the risk for ACL injury is as much as eight times higher for girls compared to boys.
The difference, it turns out, can be found in part in their genes.
Researchers from the University of Akron and Akron Children’s Hospital have discovered differences between genders in the way information is translated from genes that lead to proteins responsible for maintaining ligament structure.
This gender difference in gene expression “may account for weaker ACLs in females than males,” the researchers concluded in an abstract describing their findings.
The groundbreaking findings were presented recently at the American Academy of Orthopaedic Surgeons’ 2014 annual meeting in New Orleans.
If female athletes are indeed at a higher risk because of genetics, they can be encouraged to participate in strength training programs designed to lower the chances of ACL injuries, said Dr. Kerwyn Jones, a pediatric orthopedic surgeon at Akron Children’s Hospital who participated in the study.
“We can’t change those genes, nor should we change them,” Jones said. “But if we know these girls are going to be inherently at risk, it makes sense to me that some of these programs that have been developed, that we can institute them for all girls, starting at middle school.”
The research also could have implications beyond ACL injuries.
The findings open up the possibility that genetic differences between males and females exist for other tissues in the body, potentially making one gender more susceptive to certain injuries or illnesses than the other, said William J. Landis, University of Akron G. Stafford Whitby professor of polymer science.
“It could extend to everyday activities,” he said. “It could extend to physiological differences. It could extend to aging. It could extend to the predisposition toward cancer — all kinds of things — if you start to invoke genetics being a factor.”
The ACL is a ligament that runs diagonally in the middle of the knee, providing rotational stability. ACL ruptures can be devastating to athletes, requiring surgery to replace the torn ligament and at least six months of recovery.
Raven Pence, 15, of Akron knows the impact of ACL injuries on female athletes all too well.
Raven, a freshman at Archbishop Hoban, is recovering from surgery in February to repair her ACL, which she tore while playing basketball.
“She was at practice and going up to rebound and block a girl from shooting,” her mother, Charity, said. “When she came down on it, she twisted it wrong and it laid her out. She heard it pop.”
Raven is missing softball this spring — something that’s hard for the athletic, active teen who has played sports since elementary school.
“She’s upset, but she’s smart about it,” her mother said. “She knows she has to heal properly.”
Several ideas have been developed but never completely proven to explain why female athletes more frequently suffer ACL injuries, Jones said. Female soccer and basketball players, in particular, are at risk.
Some have pointed to hormonal difference, since ligaments are more lax during menstruation. Others explored mechanics and bone structures, noting that girls tend to be more knock-kneed than boys and land jumps with their knees straighter and closer together.
For their study, the Akron researchers examined samples from 14 young athletes — seven male, seven female — who ruptured their ACLs in non-contact sports injuries.
To the naked eye, the damaged ACL tissue from males and females looked the same, Landis said. But on a genetic level, differences between genders were discovered.
The researchers narrowed their focus to three genes that aren’t on the X- or Y-chromosomes, the sex chromosomes that differ by gender, Landis said.
The genetic differences they found between the tissue samples from male and female patients “could each significantly change the structure of the ligament so its integrity would be compromised in the women compared to the men,” he said.
According to the American Academy of Orthopaedic Surgeons, about 200,000 ACL injuries occur annually nationwide, with about half requiring reconstruction surgeries.
Cheryl Powell can be reached at 330-996-3902 or cpowell@thebeaconjournal.com. Follow Powell on Twitter at twitter.com/CherylPowellABJ.