Prior knee injury and risk of future hospitalization and discharge from military service

Background: Athletic capability is paramount for survival in military basic training and successful service. Orthopedic conditions are common reasons for hospitalization and premature discharge of military recruits. Medical fitness for military service is determined through a medical examination. Individuals medically disqualified may receive a waiver to enter the service on a case-by-case basis. This study was carried out to determine how individuals with a medical waiver for knee problems compared to recruits without a history of knee injury regarding hospitalization and military discharge. Methods: Two hundred eighty-one enlisted recruits with a history of a waiver for a knee condition were considered high risk. The comparison group was 843 recruits without prior knee pathology. Comparisons were made using frequency and chi-square analyses, relative risk estimates, and survival analyses. Results: Individuals in the high-risk group were 1.4 (CI 1.0, 2.1) times more likely to be hospitalized for any diagnoses and 8.0 (CI 2.1, 29.9) times more likely to be hospitalized for a knee condition than those in the comparison group. Individuals with a knee waiver were 2.1 (CI 1.3, 3.5) times more likely to be prematurely discharged, and 14.0 (CI 4.6, 39.6) times more likely to be discharged for a knee-related condition than those in the comparison group. Conclusion: Unfavorable outcomes were more likely in recruits disqualified initially and granted a waiver than in recruits without a history of knee injury. Military service requires intense physical activity; therefore, further research should be conducted to limit knee-related morbidity, especially in those with a prior history of knee injury.