• Knee injuries plaguing young female athletes

    August 2007 

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    Women have gained significant ground in sports since the advent in 1972 of Title IX, the federal law prohibiting sex discrimination in education. But when it comes to knee injuries, the playing field is far from level. Research has shown that girls are four to eight times more likely than boys to suffer damage to the anterior cruciate ligament (ACL), the ligament that runs from the thigh bone to the shin and stabilizes the knee. The injury most often occurs in noncontact sports when the athlete jumps or pivots.

    “Girls are four to eight times more likely than boys to suffer damage to the anterior cruciate ligament (ACL).”

    As more and more young women enter the athletic arena, ACL injuries have soared in alarming numbers. The health care costs associated with these injuries are staggering - up to $625 million annually. In addition, there are other costs to the athlete: loss of playing time, possible loss of scholarships and a greater risk for degenerative arthritis in later life.

    Effects of the menstrual cycle

    Dozens of research studies have focused on factors that put female athletes at greater risk for such injuries and on what can be done to prevent them. One theory suggests that hormones account for the gender gap in ACL injuries.

    A February 2007 review in the American Journal of Sports Medicine looked at seven studies conducted from 1998 to 2003, all examining the effect of the menstrual cycle on ACL injuries. Participants included females ages 11 to 30 in the highest-risk sports for women - basketball, skiing, soccer and handball. All of the woman had received ACL injuries while taking part in the sport. In most of the studies, the menstrual cycle phase at the time of injury was determined by interviews and blood serum or saliva tests.

    “The menstrual cycle may have an effect on ACL injury risk.”

    The conclusions of all seven studies indicated the menstrual cycle may have an effect on ACL injury risk. A common finding was that most of the injuries appeared to occur in the first half of the cycle, prior to ovulation.

    “Serum estrogen concentrations fluctuate radically throughout the menstrual cycle,” the authors of the February 2007 article state, “and estrogen has effects on muscle function and ligament and tendon strength.”

    Many of the studies also found that female athletes on oral contraceptives tended to have greater dynamic stability and passive knee stability, most likely because oral contraceptives blunt the surge of estrogen.

    Preventing ACL injuries

    According to a 2006 epidemiological study in the American Journal of Sports Medicine, research suggests that strengthening muscles and retraining athletes could cut their risks for ACL injury. The authors analyzed six research studies of interventions involving young women ages 14 through 30 who played basketball, soccer, volleyball or handball.

    In two of the studies, control groups were used to compare athletes who had pre-season neuromuscular training versus those who did not. The first of these found the rate of ACL injury was decreased 72 percent in the group of trained athletes. All of the studies found that multiple neuromuscular training reduces the risk to some degree.

    “Landing in a more bent-knee position and decelerating before a cutting maneuver appeared to have some impact on decreasing injuries.”

    High-intensity jumping plyometric movements used in training were particularly effective in preparing athletes to pivot and land safely on their feet. Implementing key techniques such as landing in a more bent-knee position and decelerating before a cutting maneuver appeared to have some impact on decreasing injuries. Balance and strengthening exercises also appeared to be helpful.

    However, as the authors of the 2006 study point out, there are attitudinal barriers to overcome. Athletes are more inclined to work harder on training that improves their performance rather than training to prevent injury. As a solution, they recommend protocols designed for both performance enhancement and ACL injury prevention techniques.

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Page last updated: 8/7/2015 2:25:23 PM
  • What the news means for you

    Cause, prevention of ACL injuries unclear

    Darren L. Johnson, MD
    Orthopaedic Surgeon

    Wright, Heather, MDThere has been a great deal of research on hormones and how they affect the strength of the collagen of the ACL, but results are not conclusive. Why female athletes have more ACL injuries and how to prevent these injures are still two major unknowns. Are the causes hormonal or structural, or is there some genetic component? More than likely, each of these factors is involved.

    “Are the causes hormonal or structural, or is there some genetic component? More than likely, each of the these factors is involved.” 

    As for a genetic risk for ACL injuries, many of the young women I treat have relatives who’ve also torn their ACL. We don’t know whether the genetic component is expressed in the collagen, in weakening the actual ligament, the way the athlete lands, how her femur or tibia is made, or her structural alignment.

    In addition, anatomy can play a part in an athlete’s risk for an ACL injury. For example, many female athletes have "miserable malalignment syndrome" - the combination of wide hips, thighs that turn inward from the hip, knock knees and flat feet, which may contribute to ACL problems.


    In the last five years, several studies have focused on the issue of prevention. Multiple groups of researchers around the country have tried to teach female athletes how to land, run and jump better. What we have found is that female athletes don’t like to bend their knees when, for example, they come down from a rebound in basketball. They like to stand very upright.

    These studies have focused on retraining the muscles that function a certain way. There’s been some encouraging data, but we need much larger studies conducted over a longer period of time. Overall, retraining is a great idea because if it helps even one person, it’s wonderful. Retraining is not invasive or harmful.

    We’re a long way from preventing ACL injuries, but early training could also help. It’s easier to teach children when they’re young, before they develop motor memory. And the focus on just one sport should be reconsidered. If you play in many different sports, you learn to use different muscle groups.

    Long-term problems

    Thirty years ago, an ACL tear was a career-ender for many athletes. Today, with the improvements in surgery and rehabilitation, many can get back into the game. But what concerns doctors in sports medicine is the long-term problem of arthritis that develops in the knee.

    One recent study followed elite female soccer players 10 years after surgery for ACL injuries. More than 80 percent of these women, all in their early 30s, had radiographic changes of arthritis. Another study looked at a group of male and female athletes seven years after ACL surgery. More than 50 percent had arthritis, and only about 50 percent were still participating in sports at the same level.

    A new surgical technique - anatomic ACL double-bundle reconstruction surgery - has the possibility of preventing these problems, but we don’t yet have long-term data on its effectiveness. The surgery is performed at only a few centers in the United States, including the University of Kentucky, because it’s more technically challenging. I do it only in select cases, such as when the ACL fails following previous surgery.

    The ACL is made up of two bundles of ligaments. Typically, surgeons have replaced the injured ligament with one bundle. This new procedure replaces both. Laboratory studies have shown that this new technique more closely reproduces normal knee motions than the traditional, more common single-bundle ACL surgery. The hope is that if we reproduce the normal anatomy of the knee better, we are going to increase the chances that the knee movements will work better and the patient won’t develop arthritis.

    “There’s a misconception... that injured athletes can go back to playing sports at pre-injury level after treatment.” 


    The majority of patients we see want to return to playing sports. If they don’t have surgery, they won’t be able to do that. However, I tell all of them, surgery is the easy part. The hardest part is mental and the will to be committed to rehabilitation.

    Unfortunately, there’s a misconception in the public that injured athletes can go back to playing sports at pre-injury level after treatment. The fact is, only 50-80 percent make it back to that level, and then only after a year of rehabilitation and therapy.

    Yet the first question the parents, the coach and the athlete ask is, "When can she return to playing?" Parents need to think about what will happen to the athlete in another 10 years. If she’s had numerous ACL injuries, they should have a conversation with her about whether she should return to the sport. As a physician, it’s my job to educate everyone involved that not all of the athletes with ACL injuries will do well.

    Dr. Johnson is professor and chairman of orthopaedic surgery and medical director of sports medicine.

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