Anterior Cruciate Ligament Injury and Safe Return to Activity in Athletes and Military

Young athletes and military members comprise a population frequently affected by anterior cruciate ligament (ACL) injury. Both are high risk for failure to return to preinjury levels of activity and reinjury. In this dissertation, we investigated trends and risk factors for ACL Injury within the US military and examined predictors of safe return to activity after ACL reconstruction (ACLR). Using a US military database, we conducted an epidemiological retrospective cohort study of US service members from 2006 to 2018 to investigate the effects of military occupation, sex, rank, and branch of service on the risk of ACL injury over time. There was a 4.1% decline in the incidence of ACL injuries with a steeper decline seen in males compared to females. The risk of ACL injury by sex was modified by rank and occupational category was a significant risk factor. Despite the decline in ACL injuries over time, the rates of ACL injury remain much higher than the civilian population. In our systematic review and meta-analysis, we investigated which measures of physical function predict return to sport and/or military duty and reinjury after ACLR. Seven studies were included and reported that activity level, lower extremity strength, hop tests, and movement quality may be important for safe return to sport. The pooled analysis indicated that individual limb performance on the side hop may provide an indication of who will return to preinjury level of sport. This study helped to inform the predictor measures included for our final aim. Finally, our prospective cohort study found that for athletes at high risk for reinjury, 63% safely returned to sport and 7% sustained a reinjury by 1 year after ACLR. Those who safely returned to sport had higher future knee self-efficacy. This body of work updated our understanding of ACL injury in the US military, reinforced the importance of psychosocial measures, and highlighted the multifactorial nature of safe return to sport after ACLR