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Quad strength indicates risk of second ACL injury

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Quadricep strength after anterior cruciate ligament (ACL) reconstruction can help predict the risk of further ACL injury, researchers have shown.

According to a study presented at the Annual Meeting of the American Orthopedic Society of Sports Medicine, young athletes who do not achieve a 90% score on six tests that measure fitness to return to athletic competition, including quadricep strength, are at increased risk for a second knee injury.

Dr Mark V. Paterno from Cincinnati Children’s Hospital and fellow researchers followed 181 patients, average age 16 years old, for two years. All participants in the study had undergone ACL reconstruction and were released to return to pivoting/cutting sports.

Each patient was given a return-to-sport assessment that included tests of isometric quadriceps strength, four functional hop tests and the International Knee Documentation Committee (IKDC) patient reported outcome survey.

The researchers wanted to find out whether successfully passing all six measures resulted in a reduced risk of second ACL injury in the first 24 months after returning to sport. They also looked at whether successfully passing individual return-to-sport criteria resulted in reduced risk of a second ACL injury.

Over the two-year follow-up period, 39 of the 181 patients suffered a second ACL injury, with 18 ipsilateral graft failures and 21 contralateral ACL tears.

At the time of the return-to-sport assessment, 57 patients had achieved 90% or greater on all testing.

Looking at the individual return-to-sport criteria, patients who failed to achieve 90% quadricep strength were 84% less likely to suffer an ipsilateral graft failure but three times more likely to suffer a contralateral ACL injury.

The researchers concluded that current criteria to evaluate young athletes’ readiness to return to pivoting and cutting sports may not identify those who are at high risk for a future ipsilateral graft tear or contralateral ACL injury.

“Further investigation is needed on the relationship between quad strength and side of future ACL injury and whether other factors may help contribute to a predictive model of future ACL injury specific to limb,” they said.