Although women are two to four times more likely than men to tear their ACL, the cause of this injury is no different between the sexes, according to new research from Duke Health published in April 2018 in The American Journal of Sports Medicine.
The findings counter a common explanation for the higher incidence of the injury in women; previous research suggested that women are more susceptible to ACL tears because their knees move differently, but researchers found that ACL tears occur the same way in women and men.
Led by biomedical engineer Louis DeFrate, PhD, the Duke team used MRI scans taken within a month of an ACL rupture, identified bruises on the surface of the femur and tibia, then used 3-D modeling and computer algorithms to reconstruct the position of the knee when the injury occurred. “Our results suggest that males and females have the same position of injury,” says DeFrate.
The study is a more rigorous forensic analysis than patient interviews and slow-motion replays of athletes’ ACL tears, which other studies have relied upon to understand the injury and possible causes for the disparity between the sexes. Some experts have also attempted to create injury prevention programs targeted at women using video replays as a template.
“Based on watching videos of athlete injuries, previous researchers have suggested that females may have a different mechanism of injury than males,” says DeFrate, “but it’s difficult to determine the precise position of the knee and the time of injury through footage.”
Because an ACL tear is such a devastating and often career-ending injury for athletes, sports programs have made considerable efforts to devise strategies for athletes to protect the ACL with strengthening and proper landing techniques, but rates of ACL injury remain high.
Using advanced imaging and modeling technology, DeFrate’s lab has produced a number of important insights about ACL injury over the past 10 years. For example, scientists have long held that valgus collapse caused the ligament to tear; however, using a forensic biomechanics approach, DeFrate’s lab concluded in a 2015 publication that landing on a hyperextended knee is actually what tears the ACL.
“In order to develop improved treatment strategies and prevention, we needed a clear understanding of what motions are most dangerous for athletes,” says DeFrate. “This work provided new evidence that landing on an extended knee may be a dangerous position for ACL tears in both males and females.”
DeFrate has worked closely with Duke Health orthopaedic surgeons, including study co-author and Duke sports medicine orthopaedic surgeon William Garrett, MD, to review and refine surgical techniques for torn ACLs. He’s hopeful that continued study of ACL injuries will lead to improvements in treatment and informed training on prevention, especially in individuals at high risk for injuries.