Changes in Physical Activity, Sleep and Knee Function After Same-Day Discharge Knee Arthroplasty

The goal of this observational study is to examine changes in physical activity, sleep quality, knee extension and flexion strength, knee range of motion, and patient-reported outcomes before and after same-day discharge knee arthroplasty (SDD-KA). The study will also investigate whether these changes are associated with each other and with patient satisfaction. As a prespecified secondary aim, researchers will compare these outcomes between patients undergoing medial unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). The main questions it aims to answer are: * How do physical activity, sleep quality, knee extension and flexion strength, knee range of motion, and patient-reported outcomes change following SDD-KA? * Are changes in these outcomes associated with each other and with patient satisfaction? * Are these outcomes different between patients undergoing medial UKA and TKA? Participants will: * Wear an accelerometer to measure physical activity and sleep before surgery, continuously from surgery to 3 months after surgery, and again for 2 weeks at 12 months after surgery * Complete questionnaires about knee function, sleep quality, pain, health-related quality of life, and satisfaction with surgery * Have knee muscle strength and active knee range of motion assessed before and 12 months after surgery * Attend follow-up assessments during the 12-month postoperative period