An ACL tear is one of the most common injuries sustained during sports. It’s estimated that 100,000 to 200,000 ACL tears occur every year in the United States, typically in basketball, soccer, and football players. ACL tears are notoriously painful and can be a career-ender in athletes if not treated properly.
Initial rest and then several weeks of rehabilitation are usually the first-line treatment for an ACL tear, but advice varies on when exactly athletes can return to the playing field. As a result, a significant number of players with ACL injuries suffer a recurrence after resuming their sport of choice.
A 2021 study published in Clinical Biomechanics may lead to a change in the rehabilitation guidelines for an ACL injury.
The study was conducted by two biomedical engineering students at Virginia Tech, Jenna Messica and Alex Peebles, along with Robin Queen, professor of biomedical engineering and mechanics in the College of Engineering. The team gathered data on 21 female athletes who had recently undergone rehabilitation for ACL reconstruction surgery. All athletes were asked to participate in hop tests, a standard test used to determine an injured athlete’s ability to return to sports. A hop test requires the athlete to perform a series of hops on both their injured and uninjured leg to compare how their performance differs by leg.
The team logged the athletes’ hop distance, hop height, peak impact force, and impulse, and the results were analyzed from two different methods of normalization — body weight and potential energy. Potential energy takes both weight and jump height into account. When comparing the two methods, they found that the results were different. That is to say, different methods of data normalization led to different interpretations of the athletes’ performance, which could affect recovery recommendations and, subsequently, their likelihood of sustaining another ACL injury upon return to their game.
“This is an important finding,” said Messica. “This research shows the value in asking more questions and analyzing the results. Overall, more than a third of athletes are tearing their ACL again after recovering. If we could better understand this and give better recommendations, we could help more athletes return to their sports safely.”
Applications for recovery guidelines
The team has expressed interest in applying their findings to clinical settings, with the goal of changing the way ACL injuries are assessed and ultimately preventing a recurrence. Physiotherapists would be able to update their recovery guidelines for ACL tears and ensure their athlete clients are completely healed before getting back to their sport.
Written by Natan Rosenfeld