Do people with preoperative mental health diagnoses experience poorer pain and functional outcomes after total knee replacement? A systematic review and meta-analysis

ObjectiveThis systematic review explored whether individuals with preoperative mental health diagnoses undergoing total knee replacement experience worse outcomes compared to patients without such diagnoses.Data SourcesMEDLINE, CINAHL, PSYCINFO, SPORT Discus, and PEDro databases were searched from inception to October 2025 to identify relevant articles.Review MethodsTwo independent reviewers screened and extracted data from relevant studies. The risk of bias for each study was assessed using the Quality in Prognostic Studies Tool. Meta-analysis using the standardized mean differences was employed to analyse associations between preoperative mental health diagnoses and pain and function at six months and ≥one year after total knee replacement. Certainty of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation tool.ResultsThe literature search yielded 53 articles eligible for the review, of which 13 were rated as low risk of bias. Preoperative mental health diagnoses were not associated with worse pain at six months (standardized mean differences = -0.68, <i>P</i> = .21) or ≥ one year (standardized mean differences = -0.48, <i>P</i> = .08) post-total knee replacement. Similarly, preoperative mental health diagnoses were also not associated with functional outcomes at six months (standardized mean differences = -0.34, <i>P</i> = .07) or ≥one year (standardized mean differences = -0.56, <i>P</i> = .32). Considerable heterogeneity and imprecise estimates limited the certainty of these findings.ConclusionFindings suggest that preoperative mental health conditions alone may not predict poor pain and function outcomes post-total knee replacement. Given the heterogeneity and low certainty of evidence, further research should explore associations between mental health and other risk factors to guide personalized preoperative interventions.