Same day discharge (SDD) following total hip and knee arthroplasty (THA and TKA) increased significantly during the COVID-19 pandemic across Ontario. This practice has been facilitated by advances in both orthopaedic and anesthesia techniques. Although SDD is an appealing strategy for resource constrained health systems, the practice may invoke unintended consequences. In this study we wanted to examine whether the drive to SDD during the pandemic has lead to fewer vulnerable patients (i.e. those with medical comorbidity and social marginalization) receiving hip and knee arthroplasty as compared to prior to the pandemic. We conducted a population-based, retrospective cohort study of all patients undergoing primary THA and TKA in Ontario between 2017 to 2021. Data was extracted from the ICES database and previously validated algorithms were utilized to identify patients and variables. All patients undergoing primary total hip or knee arthroplasty treated by all surgeons and hospitals in Ontario during the study period were included. We excluded revision arthroplasties and other arthroplasty operations (ex. partial knee replacements). Patients were grouped into ‘pre-covid’ and ‘post-covid’ eras based on when surgery was performed. “Pre-covid' was defined as THA or TKA surgery occurring before the government-mandated cancellation of elective surgery in Ontario on March 15, 2020. Surgery during the “post-covid” era was defined as occurring after the gradual reopening of elective surgery in Ontario on May 26, 2020. Patients receiving surgery between these government-mandated shutdown dates were also excluded. Validated measures of patient comorbidity and socioeconomic status during the ‘pre-covid’ and ‘post-covid’ eras were compared using appropriate statistical tests. There were 42,644 patients receiving THA in Ontario between 2017 and 2021 (27,796 in the pre-covid era and 14,848 in the post-covid era). As compared to THA patients in the pre-covid era, patients in the post-covid era were significantly less likely to be have CHF (p<.001), Hypertension (p<.001), COPD (p<.001), Diabetes (p<.001), Rheumatoid Arthritis (p<.001), and Frailty (p<.001). Post-covid THA patients were also more likely to be in the highest income quintile (p<.001) as compared to pre-covid patients. There were 59,801 patients receiving TKA in Ontario between 2017 and 2021 (41,441 in the pre-covid era and 18,360 in the post-covid era). As compared to TKA patients in the pre-covid era, patients in the post-covid era were also significantly less likely to be have CHF (p<.001), Hypertension (p<.001), COPD (p<.001), Diabetes (p<.001), Rheumatoid Arthritis (p<.001), and Frailty (p<.001). Post-covid TKA patients were also more likely to be in the highest income quintile (p<.001) as compared to pre-covid patients. We found significantly fewer vulnerable patients (i.e. those with medical comorbidity and social marginalization) receiving hip and knee arthroplasty across Ontario during the pandemic in Ontario as compared to prior. This phenomenon may be explained, at least in part, by patients with comorbidities electing nonoperative treatment due to perceived medical risk of surgery during the pandemic. However, the observed trends occurred at the same time as SDD expanding significantly across the province which likely has also contributed to the selection of healthier, less marginalized patients who can be discharged safely on an outpatient basis at the exclusion of other patients. These preliminary findings point to a need for further monitoring of whether this trend continues and mitigation strategies to ensure more vulnerable patients, some of whom are most need of surgery, are not being left behind.