The Association Between History of an Ankle Sprain and Traumatic Meniscal Injury Among Infantry Combat Soldiers in the Israeli Defense Forces: A Historical Cohort Study

INTRODUCTION: The high frequency and number of ankle inversion injuries and meniscal injuries in military populations is an area of concern due to the debilitating effects and cumulative consequences of these particular injuries on the soldiers sustaining injury and the consequences on the operational effectiveness of the Israeli Defense Force (IDF). This study examines the possible relationship between ankle inversion injury and potential for subsequent meniscal injury in infantry soldiers in the IDF. MATERIAL AND METHODS: All 89,069 infantry combat soldiers (including special units), recruited to the IDF between 2007 and 2017 were included in this study. A historical cohort study was conducted. The cohort was divided into two groups: The exposure group included all participants that had suffered at least one ankle sprain in the past and the unexposed group that included all participants who did not suffer an ankle sprain in the past. A Cox proportional-hazards model (COX) model was used in order to obtain the adjusted to confounders association between exposure and outcome expressed in hazard ratio (HR). RESULTS: The crude association between ankle sprain in the past and the development of meniscal injury in this study was 0.87 (Relative risk = 0.87, P = 0.007). After adjusting for unit type, Body Mass Index (BMI), previous fracture of the lower limb, and the use of eyeglasses, using a COX model, the adjusted association between ankle sprain in the past and the development of meniscal injury was 0.8 (HR = 0.8, P = 0.001, confidence interval (95%) 0.74, 0.88). CONCLUSION: The results of this study indicate ankle sprains to be a protective factor for meniscal injury. Our main conclusion from the results of this study is that the assumption that those with previous leg injuries are at a greater risk for further leg injuries is questionable and cannot be generalized. Hence, the association between different types of injuries should be investigated separately.