<p>This prospective study of 123 patients examined the relationship between mental health and the recovery process in terms of pain, function, and quality of life up to one year after total knee arthroplasty (TKA). Mental health questionnaires such as the Hospital Anxiety and Depression Scale (HADS) and the Beck Depression Inventory Fast Screen (BDI-FS) were completed pre-operatively as well as at three months and 12 months post-operatively. In addition, patient-reported outcome measures such as the Oxford Knee Score (OKS), EuroQol-5 Dimensions (EQ-5D-3&#xa0;L), and pain intensity were examined to determine the association between functional and psychological symptoms. There were no significant correlations between pre-operative mental health and post-operative outcomes at three months. However, at 12 months follow-up, preoperative anxiety and depression correlated with worse pain, function, and quality of life scores. Group comparisons with groups defined by the cut-off ranges of the psychological health scores also showed these differences. Additionally, poor outcomes for joint function, quality of life, and pain were associated with high depression scores at 12 months post-operatively. This study highlights the importance of pre-operative mental health for the success of TKA, but also the association between poor functional outcomes and mental health post-operatively.</p>