BACKGROUND: The benefits of combining enhanced recovery after surgery (ERAS) interventions with an outpatient program for total hip/knee arthroplasty (THA/TKA) are uncertain. The primary objective was to compare adverse event rate and secondly to compare pain management, functional recovery, PROMs and satisfaction in patients who experienced both an ERAS-outpatient protocol and standard-inpatient care.METHODS: We conducted an ambidirectional single subject cohort study on 48 consecutive patients who experienced both a standard-inpatient and an ERAS-outpatient THA/TKA (contralaterally). We compared complications according to Clavien-Dindo scale and Comprehensive Complications Index (CCI), and unplanned episodes of care. Postoperative pain assessed with a numeric rating scale, opioid consumption in morphine milligram equivalents, functional recovery, patient-reported outcome measures (WOMAC, KOOS, HOOS, Forgotten Joint Score and Patient Joint Perception) and patients’ satisfaction were also evaluated.RESULTS: Following the ERAS-outpatient surgery, complication rates were reduced by more than 50% (2.1 vs 4.4, p<0.001), CCI was significantly lower (12.3 vs 19.1, p<0.001), and similar unplanned episodes of care were observed (p>0.999). In the first 8 postoperative hours, perceived pain was similar (p>0.805) while opioid consumption was significantly reduced (9.3 vs 26.5, p<0.001). Patients walked, climbed stairs, showered, performed activities of daily living, practised sports, went back to work sooner (p<0.001), but PROMs were similar between groups at the last follow-up (p> 0.188). Patients were more satisfied of the ERAS-outpatient pathway and recommended it significantly more (p <0.002). CONCLUSION: Compared to the conventional inpatient care, our ERAS-outpatient protocol proved to be safer, enable faster functional recovery, and improve patients’ satisfaction which highlight the importance of following ERAS principles when implementing an outpatient THA/TKA program.