The medial longitudinal arch as a possible risk factor for ankle sprains: a prospective study in 83 female infantry recruits.

BACKGROUND: Ankle sprains are frequent, especially in athletes, soldiers, or others who perform high levels of physical activity. Although prevention is a primary goal, little is known about the risk factors. We evaluated the association of the structure of the medial arch of the foot to the occurrence of acute and recurrent ankle sprains in 83 female infantry recruits. We found no previous studies on ankle sprains in women in the English literature.
METHODS: Arch height was quantified using the Chippaux-Smirak index, and each arch was classified as high, normal, or low. Retrospective data were obtained from questionnaires in which the soldiers noted whether or not they had had ankle sprains in the past, the grade of the sprain, and recurrence. Prospective data were accumulated in the 4 months of basic training, during which time every ankle sprain was documented and classified according to its grade and cause.
RESULTS: The retrospective data showed more frequent ankle sprains in the low arch group than in the normal arch group, mainly in the right foot (RR of 2.9, p <0.05). Recurrent sprains studied retrospectively also showed that more sprains occurred in the low arch group than in the normal arch and high arch groups (RR of 10.3, p <0.05). The prospective data suggested a pattern toward the same outcome (50% in the low arch as opposed to 36% in the normal arch group, RR, 1.3), but with no statistical significance.
CONCLUSIONS: We concluded that a low arch of the foot might be a risk factor for ankle sprains. However, our study consisted of a relatively small population, and further studies are needed.