A Comparison of Heart Rate Variability Biofeedback, Mindfulness, and Psychoeducation-based Interventions on Clinical Recovery Outcomes in Patients Undergoing Total Knee Arthroplasty

The goal of this clinical trial is to compare the effects of heart rate variability biofeedback (HRVB), mindfulness meditation, and psychological education in patients undergoing total knee arthroplasty (TKA). Patients waiting for TKA often experience anxiety, pain, and sleep problems before surgery. These factors may affect recovery after surgery. HRVB and mindfulness have been used to reduce stress and anxiety in different patient groups, but few studies have directly compared these approaches in patients undergoing TKA. The main questions this study aims to answer are: * Does HRVB improve postoperative recovery, including pain, sleep quality, quality of life, and knee function, compared with mindfulness meditation and psychological education? * Do HRVB and mindfulness meditation reduce preoperative anxiety more effectively than psychological education? * Are changes in heart rate variability and EEG measures related to recovery outcomes after surgery? Researchers will compare HRVB, mindfulness meditation, and psychological education to evaluate their effects on anxiety reduction and postoperative recovery. Participants will: * Be randomly assigned to one of three groups: HRVB, mindfulness meditation, or psychological education. * Receive one 15-minute intervention session before surgery. * Continue home-based practice during the first 2 weeks after surgery while following routine rehabilitation exercises. * Complete assessments before surgery and at 2, 6, and 12 weeks after surgery. The assessments will include measures of anxiety, pain, sleep quality, quality of life, knee function, heart rate variability, and EEG activity.