Reducing forces to the knee may reduce the risk of ACL injuries

The anterior cruciate ligament may be vulnerable to injury, especially in female athletes, but some exercise and stretching programs are designed to help stabilize and strengthen the knee ligament. A new training program focusing on decreasing the shear forces on knee joints may help prevent future ACL tears.

The study involved 14 female high school and college basketball players who had no prior knee injuries. As they performed jump-stop movements (like those done in basketball drills) they were fitted with implements that allowed researchers to measure their movements, muscle activity, and the forces applied to their knee joints.

The athletes were first asked to do the exercise with their normal movements. They were then instructed to do the same movement but with an alternate technique--jumping higher and landing more steeply, bending the knees more before taking off, and landing on their toes.

All of the athletes reduced the force to the knee that occurs on landing (when forces are passed through the tibia) by an average of 56%. Many ACL injuries occur while landing and pivoting, not just after colliding with another player.

A couple of caveats to the study: co-author David Hawkins, professor of neurobiology, physiology and behavior at UC Davis, says the results don’t show that the modified jumping and landing techniques will reduce ACL injuries. Also, practicing techniques in a lab is one thing, and playing in a competition is another. Hawkins said that during actual play, athletes may fall back on muscle memory, slipping into old habits. More training and practice might correct that.

In the study, the authors wrote, “While the current ACL injury prevention programs include some landing mechanics instruction, there is evidence to suggest that a greater emphasis on landing mechanics, coupled with the benefits of increased muscle strength and activation that have been demonstrated, can provide these programs with a better chance of lowering ACL injury risk.”

The study appeared online recently in the Journal of Biomechanics.

- Jeannine Stein / Los Angeles Times