The incidence of post-operative delirium in the South-east Asian population is not known. Through a prospective, single centre, observational study, the investigators aim to characterize the incidence and risk factors of delirium in older adults undergoing elective total joint arthroplasties (TJA). The study will recruit eligible patients (65 - 90 years old undergoing elective TJA), with a targeted sample size of 500. Patients will be screened for dementia and Confusion Assessment Method (CAM) scores obtained pre and post operatively. Other data such as preoperative Charlson comorbidity index (CCI), post op complications using Post operative Morbidity Survey (POMS), pain scores, readmission rates and length of hospital stay (LOS), functional and health-related quality-of-life (HRQoL) will also be collected and analysed.