Many factors are thought to cause ankle ligament injuries. The purpose
of this study was to examine injury risk factors prospectively and de
termine if an abnormality in any one or a combination of factors ident
ifies an individual, or an ankle, at risk for subsequent inversion ank
le injury. We examined 145 college-aged athletes before the athletic s
eason and measured generalized joint laxity, anatomic foot and ankle a
lignment, ankle ligament stability, and isokinetic strength. These ath
letes were monitored throughout the season. Fifteen athletes incurred
inversion ankle injuries. Statistical analyses were performed using bo
th within-group (uninjured versus injured groups) data and within-subj
ect (injured versus uninjured ankles) data. No significant differences
were found between the injured (N = 15) and uninjured (N = 130) group
s in any of the parameters measured. However, the eversion-to-inversio
n strength ratio was significantly greater for the injured group compa
red with the uninjured group. Analysis of the within-subject data demo
nstrated that plantar flexion strength and the ratio of dorsiflexion t
o plantar flexion strength was significantly different for the injured
ankle compared with the contralateral uninjured ankle. Individuals wi
th a muscle strength imbalance as measured by an elevated eversion-to-
inversion ratio exhibited a higher incidence of inversion ankle sprain
s. Ankles with greater plantar flexion strength and a smaller dorsifle
xion-to-plantar flexion ratio also had a higher incidence of inversion
ankle sprains.