The aim of this study is to determine the prevalence and correlates of major depression, generalized anxiety disorder, and panic disorder in patients scheduled for knee arthroplasty. Three hundred nine patients completed questionnaires and validated self-report measures of major depression, generalized anxiety, and panic disorder. Stepwise multivariable logistic regression identified preoperative predictors of major depression and generalized anxiety disorder. The prevalence of major depression was 22.5% (95% confidence interval [CI], 18%-28%). For generalized anxiety disorder, prevalence was 20.2% (95% CI, 16%-25%), and for panic disorder, prevalence was 4.6% (95% CI, 2.8%-7.6%). Multiple predictors for major depression and generalized anxiety disorder were found. Major depression and generalized anxiety are relatively common among patients scheduled for knee arthroplasty. Several simply assessed variables can be used to identify patients who are likely to have major depression or generalized anxiety.