Risk factors for noncontact ankle sprains in high school football players: the role of previous ankle sprains and body mass index.

BACKGROUND: In a previous study, we noted a possible connection between an athlete's weight and risk of ankle sprain.

HYPOTHESIS: A high body mass index and a history of a previous ankle sprain increase the risk of a subsequent noncontact sprain.

STUDY DESIGN: Cohort study; Level of evidence, 2.

METHODS: One hundred fifty-two athletes from 4 football teams were observed (2 varsity and 2 junior varsity). Two teams were observed for 3 seasons, and 2 teams were observed for 1 season. Before each season, body mass, height, history of previous ankle sprains, and ankle tape or brace use were recorded.

RESULTS: There were 24 ankle sprains, of which 15 were noncontact inversion sprains (11 grade I, 3 grade II, 1 grade III; incidence, 1.08 per 1000 athlete-exposures). Injury incidence was higher in athletes with previous ankle injuries (2.60 vs 0.39; P < .001). Body mass index was also a risk factor (P < .05): injury incidence was 0.52 for players with a normal body mass index, 1.05 for players at risk of overweight, and 2.03 for overweight players. Injury incidence was 0.22 for normal-weight players with no previous ankle sprain compared with 4.27 for overweight players who had a previous sprain.

CONCLUSION: An overweight player who had a previous ankle sprain was 19 times more likely to sustain a noncontact ankle sprain than was a normal-weight player with no previous ankle sprain.

CLINICAL RELEVANCE: Ankle sprain prevention strategies should be targeted at football players with a high body mass index and a history of previous ankle sprains.