Female athletes and ACL injuries: A look at factors that may contribute
On a yearly basis, at least 100,000 people nationwide suffer from an ACL injury, more than half of which require surgery. Some studies show female athletes on a collegiate level to be three times more likely to incur an ACL tear than males, while others report that female high school athletes are five times more likely than males to suffer from a knee injury. With ACL injuries rising in prevalence, it has become common knowledge that they result from an assortment of factors; however, the specific factors associated with ACL tears and other injuries are yet to be examined in full detail.
In order to better understand some of the contributing factors associated with these injuries, a study was performed to analyze the relationship between ACL injury history and an assortment of factors that may or may not have been linked to the injuries, including prior ankle injury, a suspicious candidate. The subjects of the study were 33 physically active females who had a history of ACL injury in the past five years, with an additional 33 female athletes without injury used as controls. Each of the subjects completed a survey about their knee and ankle history, then underwent a series of 16 tests that measured laxity, malalignment, flexibility and postural control. Generalized laxity was assessed using the Beighton laxity scale, in which a medical professional noted the presence (or lack thereof) of laxity by visual observation. To determine lower extremity malalignments, a number of assessments were made that included foot type, leg length, pelvic tilt and genu recurvatum, which measures the backward curvature, or hyperextension of the knee. For lower extremity range of motion and flexibility, the grouping included the 90/90 test, the Thomas test and the Ober's test on both limbs of all subjects, each of them measuring a different element of flexibility or range of motion. The Ober's test measured iliotibial band (ITB) and tensor fascia latae (TFL) flexibility, which are both located in the thigh. For postural control, static balance was determined with the balance error scoring system and dynamic balance with the anterior reach component of the star excursion balance test.
The results from each assessment were analyzed, and the ones showing no correlation to ACL injury were removed from the study. Final results showed a significant association between ACL injury history and ankle sprain history, as those with a history of ACL sprain were more likely to also have a history of ankle sprain(s). Of the 66 limbs of subjects with ACL injury history, 31 (47%) had a previous history of ankle injury, while only 21 (32%) of the 66 uninjured limbs had also suffered an ankle injury. This connection may be explained by the relationship between the hip, knee and ankle, as each of the three has an influence on the other. Injured ankles are likely to affect gluteus maximus activity, which in turn could affect gait pattern and therefore put the knee at a higher risk of injury.
Aside from ankle history, three additional factors showed a significant relationship to ACL injury history: increased generalized laxity, increased genu recurvatum and decreased ITB flexibility. It has been suggested by some that females generally have "looser" joints compared to males, and thus are more prone to suffer from an ACL injury. A separate study that followed both male and female basketball players over two years concluded that the females who sustained the most ligament sprains did in fact have "looser" joints than others, and therefore had increased generalized joint laxity. Increased genu recurvatum proves to also be a predictor of ACL injury, as knee hyperextension may produce tension on the ACL and can make hamstrings less efficient by placing them in an elongated position. Decreased ITB flexibility also proved a consistent indicator of ACL injury, and may stem from too much tension within the ITB and TFL, which affect the ACL. In total, the factors investigated in the study explained 35.2% association of ACL group membership. The underwhelming percentage exemplifies the necessity that numerous additional factors be analyzed in greater detail in order to further concentrate on the specific contributing factors related to ACL injury. Also, the link that likely exists between ACL and ankle injury history should alert physical therapists to revamp ankle rehabilitation programs to incorporate preventative methods against ACL injury.
-As reported in the December, '07 edition of Journal of Sports Medicine and Physical Fitness
-By Greg Gargiulo
