Predicting ACL Outcomes: Biomechanics
Some people who undergo surgical ACL repairs continue to experience symptoms for months or even years afterward—and others don’t. New research suggests a reason why.
A torn ACL is probably high on your athletes’ lists of things they hope to avoid—and for good reason. Surgery to repair the ligament is painful enough, but frequently, healing from the surgery doesn’t mean the end of the pain. In fact, a third of all ACL reconstruction patients go on to develop osteoarthritis within 10 years, while almost half will have it within 20 years. So why do some people continue to suffer, while others end up pain free?
New research conducted by the University of North Carolina and Brigham Young University suggests that the answer may lie in an individual’s biomechanics, according to a recent report by ScienceDaily. The researchers sorted 130 people who had had ACL reconstruction surgery into two groups based on whether or not they still were still experiencing symptoms. Then they asked the subjects to walk barefoot over a force plate while they measured ground reaction forces.
People who still had symptoms were found to be under-loading or overloading their injured leg by four to five percent. Those with more recent surgeries under-loaded, while those with less recent surgeries were more likely to overload.
While four to five percent might not seem like much, researchers believe it’s significant enough to factor heavily into surgical outcome. “At first look, these changes are relatively small,” said Brian Pietrosimone, PhD, ATC, Associate Professor of Athletic Training and Co-Director of the Neuromuscular Research Laboratory at the University of North Carolina and lead author on the study. “Yet when you think about a [five] percent difference every step you take every day, over the course of a month, year, or lifetime, you can extrapolate why a seemingly small change could lead to a progressive and chronic disease like post-traumatic osteoarthritis.”
The solution, according to the study’s authors, is twofold. First, individuals who undergo ACL repair should take steps to restore their movement mechanics afterward, including ramping up physical therapy and strength training. Second, the scientific community needs to conduct further research into what exactly it is about differences in post-surgery biomechanics that predicts whether individuals will end up with osteoarthritis or escape it.
“ACL reconstruction is fairly effective, but some people don’t ever fully recover,” said study co-author Matt Seeley, PhD, ATC, Associate Professor of Exercise Sciences at BYU. “The way you move is related to the outcome of your ACL surgery.
“These data indicate overloading and underloading are likely deleterious to cartilage,” he continued. “This study sets the table for a longitudinal study to determine the precise causes of altered leg biomechanics post-surgery.”
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