Structural and Functional Brain Differences Related to Recurrent Shoulder Instability: A Systematic Review.

OBJECTIVE: To explore (1) structural and functional brain changes associated with recurrent shoulder instability (RSI) and (2) their associations with clinical outcomes. DESIGN: Systematic review of observational and case-control studies. LITERATURE SEARCH: A comprehensive search was conducted in PubMed, Web of Science, and EMBASE for articles published up to December 2023. Reporting was guided by the PERSiST (implementing Prisma in Exercise, Rehabilitation, Sport medicine and SporTs science) and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 guidelines. STUDY SELECTION CRITERIA: Peer-reviewed observational and case-control studies were eligible if they included individuals with RSI and assessed structural or functional brain changes using neuroimaging. DATA SYNTHESIS: The internal validity of included studies was evaluated using the National Heart, Lung, and Blood Institute's Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies and Quality Assessment of Case-Control Studies. Outcomes were synthesized qualitatively due to heterogeneity in imaging protocols and outcome measures. RESULTS: Seven studies met the inclusion criteria, involving 100 patients with RSI and 70 healthy controls. Structural brain differences assessed via voxel-based morphometry were not significant in 3 studies but were significant in 1 study. Six studies reported consistent patterns of neuroplasticity in functional brain outcomes, with increased functional connectivity in the primary sensorimotor cortex, dorsolateral prefrontal cortex, and anterior insula. Four studies identified significant correlations between brain connectivity measures and clinical scores, suggesting a link between sensorimotor and emotion-regulation networks and functional outcomes in RSI. CONCLUSION: Functional, rather than structural, brain alterations appeared to be involved in RSI. These findings support the relevance of central mechanisms in RSI and require confirmation through longitudinal designs and larger cohorts. JOSPT Open 2026;4(2):133-154. Epub 6 February 2026. doi:10.2519/josptopen.2026.0157.