Many factors are thought to cause ankle ligament injuries. The purpose of this study was to examine injury risk factors prospectively and determine if an abnormality in any one or a combination of factors identifies an individual, or an ankle, at risk for subsequent inversion ankle injury. We examined 145 college-aged athletes before the athletic season and measured generalized joint laxity, anatomic foot and ankle alignment, ankle ligament stability, and isokinetic strength. These athletes were monitored throughout the season. Fifteen athletes incurred inversion ankle injuries. Statistical analyses were performed using both within-group (uninjured versus injured groups) data and within-subject (injured versus uninjured ankles) data. No significant differences were found between the injured (N = 15) and uninjured (N = 130) groups in any of the parameters measured. However, the eversion-to-inversion strength ratio was significantly greater for the injured group compared with the uninjured group. Analysis of the within-subject data demonstrated that plantar flexion strength and the ratio of dorsiflexion to plantar flexion strength was significantly different for the injured ankle compared with the contralateral uninjured ankle. Individuals with a muscle strength imbalance as measured by an elevated eversion-to-inversion ratio exhibited a higher incidence of inversion ankle sprains. Ankles with greater plantar flexion strength and a smaller dorsiflexion-to-plantar flexion ratio also had a higher incidence of inversion ankle sprains.

Over two million individuals suffer ankle ligament trauma each year in the United States, more than half of these injuries are severe ligament sprains; however, very little is known about the factors that predispose individuals to these injuries. The purpose of this study was to determine the risk factors associated with ankle injury. We performed a prospective study of 118 Division I collegiate athletes who participated in soccer, lacrosse, or field hockey. Prior to the start of the athletic season, potential ankle injury risk factors were measured, subjects were monitored during the athletic season, and injuries documented. The number of ankle injuries per 1000 person-days of exposure to sports was 1.6 for the men and 2.2 for the women. There were 13 injuries among the 68 women (19%) and seven injuries among the 50 men (1 3%), but these proportions were not significantly different. Women who played soccer had a higher incidence of ankle injury than those who played field hockey or lacrosse. Among men, there was no relationship between type of sport and incidence of injury. Factors associated with ankle ligament injury differ for men relative to women. Women with increased tibia1 varum and calcaneal eversion range of motion are at greater risk of suffering ankle ligament trauma, while men with increased talar tilt are at greater risk. Generalized joint laxity, strength, postural stability, and muscle reaction time were unrelated to injury.

In this study of first-time ankle sprains, for most sports, the incidence rate of inversion injury is less than 1 per 1000 days of exposure to sport, a value lower than previously reported. Among female athletes, ankle injury is associated with type of sport. Risk is highest for female basketball athletes, who are at significantly greater risk than male basketball athletes and female lacrosse athletes. The risk of first-time ankle injury is similar for high school and college-level athletes.

Severe ankle injuries can require extended periods of immobilization that adversely affect the strength of the ankle muscles. We have investigated a single-leg strength training program of the muscles surrounding the ankle to determine if it produces a crossover benefit for the contralateral ankle muscles. Twenty subjects without any history of ankle injuries were randomly divided into a control and a training group. Both groups underwent isokinetic testing of the ankle muscles at the beginning and end of an 8-week period. The control group maintained normal activities between the tests. Half of the training group trained the dominant leg only and the other half trained the nondominant leg only for the 8-week period, three times per week. The subjects who trained the dominant leg improved peak torque values by 8.5% in the trained leg and 1.5% in the untrained leg. Similarly, the subjects who trained the nondominant leg improved peak torque values by 9.3% in the trained leg and 3.5% in the untrained leg. In contrast, the control group showed no significant change in peak torque, power, or endurance between the initial and final tests. With improvements in peak torque as high as 40% in the trained leg and a crossover benefit of 19% in the untrained leg in eccentric inversion, this strength training technique deserves further investigation in an injured population where the benefits may be more substantial.

Ligamentous instability, ankle muscle weakness, foot-ankle alignment, and generalized joint laxity may be predisposing factors for ankle ligament injuries. The purpose of this study was to examine the reliability of these risk factors before and after the season in healthy individuals and to determine if any significant differences developed during the athletic season (range, 12 to 16 weeks). Twenty-one healthy college-aged athletes were tested for generalized joint laxity, anatomic alignment of the foot and ankle, ligamentous stability, and isokinetic strength of the ankle muscles. This study showed that generalized joint laxity, ankle ligamentous stability, and ankle strength measurements demonstrated high correlation coefficients (r > 0.75). The high correlation coefficients suggested reliable measures. Some of the range of motion measurements had lower correlation coefficients, which suggested more variability in these measurements. After establishing the reliability in 24 of the 28 measurements with standardized methods, further work is underway to evaluate the role of these factors in inversion ankle sprains.