Risk Factors for Glenohumeral Joint Instability in Service Academy Cadets: An Analysis of Baseline Demographics and Injury History- MHSRS 2026

j dowe, m aderman, m bradley, a hartin, j robins, t dekker, r waltz, l leclere, m slabaugh, s gee, m donahue, k cameron, j dickens

Abstract accepted for poster presentation at the 2026 Military Health System Research Symposium (MHSRS)

INTRODUCTION: Compared to the general population, US service academy members have a 20x higher risk of sustaining a shoulder instability event during their time of enrollment. With such prevalence exists an impact on military medical readiness, necessitating the need to identify and treat this common condition efficiently to optimize recovery. This study aims to understand the relationship between demographic and injury history variables and the incidence of future instability events.

MATERIALS AND METHODS: This prospective cohort study recruited cadets entering their first-year at the US Air Force Academy. Demographic, health history, and sports participation information was collected at the time of enrollment. Those who experienced glenohumeral joint instability (GHJI) events during their time at the academy were identified and followed for additional analysis. Univariate and multivariable logistic regression models were used to assess the association between potential risk factors and incidence of injury. Statistical significance was set at p<0.05.

RESULTS: 1,445 participants (41.11% female; 18.93±1.00y; 175.14±10.01 cm; 71.53±12.03 kg) completed baseline demographics and injury history. 49 individuals (58.06% female; 20.62±1.23y; 176.09±9.22 cm; 73.21±12.82 kg) were identified as having experienced GHJI during the surveillance period. Of those injured, 10 experienced multiple instability events (5 bilateral, 5 unilateral), resulting in a total of 59 instability events for analysis. 33 of the injuries were subluxations, and 26 were dislocations of the shoulder. Indication of a history of shoulder instability at baseline was the key factor significantly associated with a 2.82x increased likelihood of subsequent injury (OR=2.82; 95% CI, 1.33-5.99; p=0.007). Additionally, participation in an overhead sport (OR=1.71, p=0.094) and a history of previous shoulder surgery (OR=6.82, p=0.068) showed positive trends toward an increased chance of injury. No significant association was found for sex, or subjective feelings of instability.

CONCLUSIONS: As shoulder instability is a known threat to readiness and delayed return to duty, it is essential to place those at higher risk in a position to succeed through proper recognition and treatment. Applying this knowledge early in a service member’s career may increase longevity and further enhance duty capabilities. Addressing key factors associated with GHJI is critical for future duty optimization.