NEW YORK (Reuters Health) – Despite research suggesting women’s knees are more prone to ligament injuries, a new Swedish study finds that men in that country have more anterior cruciate ligament (ACL) tears, and more surgeries to fix them, than Swedish women.
The report, published online June 8th in the American Journal of Sports Medicine, is the first to count ACL injuries across the entire Swedish population – not just among players of particular sports, or in certain regions – which may help explain the findings, according to the authors.
“I think the difference is that earlier studies studied at-risk populations. In those studies, women are more prone to get injured. The difference with this study is that we studied the general population,” said Dr. Richard Nordenvall, of Karolinska University Hospital in Stockholm.
In the U.S., an estimated 80,000 cruciate ligament injuries (the majority, ACL) occur every year, and almost half are surgically repaired.
Data for Sweden were incomplete, so Dr. Nordenvall and his colleagues used a nationwide database of patients to see how many Swedes had knee ligament injuries and how many had surgical repairs between 2002 and 2009.
Overall, 56,659 people in Sweden tore a knee ligament during the study period. The researchers say that works out to an average of 78 tears for every 100,000 Swedish citizens.
Men accounted for about 34,000 of those tears, or 60%. Men also had 59% of the reconstructive surgeries associated with knee ligament injuries.
Swedish women tended to experience ACL injuries at a younger age (between ages 11 and 20, versus 21-30 for men).
When Dr. Nordenvall and his colleagues looked just at the age groups with the highest injury rates, men still had far more knee troubles. The numbers worked out to about 144 tears per 100,000 women between 11 and 20 years old, and 225 tears per 100,000 men aged 21-30.
Dr. Darin Padua, director of the Sports Medicine Research Laboratory at the University of North Carolina at Chapel Hill, said he was not surprised by the findings.
The evidence that women are more prone to ACL injuries is fairly specific to sports, not to the general population, explained Dr. Padua, who was not involved in the new research.
No one can say for certain why women seem to tear their knee ligaments earlier in life compared to men, Dr. Padua added, but he said it probably has to do with body development and movement patterns.
What was uniform among both men and women in the Swedish study was the proportion opting for surgical ACL reconstruction: about 36% of patients of each gender.
Those who chose surgery, however, tended to be younger than those who didn’t (mean age, 27 vs 35).
For Dr. Nordenvall, the next step is to see what happens in those who have surgery.
“I am right now studying if reconstruction of the cruciate ligament prevents development of osteoarthritis,” he told Reuters Health.
But he said it’s important for people to know how common the injury is.
“It’s a common injury and it’s more common than what has been thought of earlier,” he said.
Dr. Padua noted this study also helps to illustrate the point that both men and women should be taking part in injury prevention programs, many of which are accessible online, including one available for free on the University of North Carolina’s Web site (http://bit.ly/PeLO29).
Am J Sports Med 2012.