Last Updated: 2008-06-26 13:01:12 -0400 (Reuters Health)
By Amy Norton
NEW YORK (Reuters Health) - Young female athletes who have loose joints may be at greater risk of tearing the anterior cruciate ligament in the knee, a new study suggests.
The ACL is a tough band of tissue that runs from the thigh bone to shin bone, playing an important part in stabilizing the knee joint. When it tears, it's often the result of a sudden, forceful twist -- such as an awkward landing from a jump that torques the knee.
It's long been known that female athletes are much more likely than their male counterparts to tear the ACL.
The new findings, based on more than 1,500 teenage female athletes, suggest that joint "laxity" may contribute to their risk of ACL injuries.
Researchers found that young women whose knee ligaments tended to be less taut, and who therefore had less-stable knee joints, were at greater risk of suffering an ACL tear over four years.
In particular, there was a five-fold higher risk of ACL tears among athletes whose knees were hyperextended -- meaning that when the leg is straight, the knee joint goes beyond a neutral alignment and bows backward.
The findings are published in the American Journal of Sports Medicine.
After puberty, ligament laxity and joint flexibility tend to increase in females and decrease in males -- a difference that might factor into female athletes' higher rate of ACL tears.
"There are many factors that contribute to (the risk of ACL tears), and this might be one of them," lead researcher Gregory D. Myer, of Cincinnati Children's Hospital, told Reuters Health.
Nothing can be done to change ligament laxity, Myer explained, but certain training techniques may help reduce athletes' risk of ACL tears -- something that might be especially important for those with greater laxity in the knee joint.
For example, learning how to land from a jump with proper alignment, and not in a "knock-kneed" position, may help prevent ACL injuries.
In addition, strengthening the hamstring muscles, which help stabilize the knee joint, appears particularly important, according to Myer.
He said he and his colleagues are continuing to investigate the types of exercises that are most effective at lowering the risk of ACL tears. Exercises that go beyond the knee and focus on building strength in the hips and "core" of the body are also showing promise.
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SOURCE: American Journal of Sports Medicine, June 2008.