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Background The adductor canal block (ACB), known for its motor-sparing properties, has gained popularity as part of the multimodal analgesic regimen in total knee arthroplasty (TKA) patients. However, the duration of single-injection blocks is limited, potentially contributing to rebound pain after the first 24 hours. This study evaluates whether extending block duration using a continuous peripheral nerve catheter reduces opioid consumption during the 24–48 hour period following TKA.Methods This participant-blinded and assessor-blinded randomized controlled trial included 94 patients undergoing primary, unilateral TKA. Patients were randomized into two groups: the single-injection group received a single-injection ACB (15 mL of 0.25% bupivacaine) with 2 mg perineural dexamethasone; the continuous infusion group received a single-injection ACB (15 mL of 0.25% bupivacaine) followed by a continuous adductor canal catheter infusing 0.2% ropivacaine at 8 mL/hour for 50 hours. Both groups received a standardized multimodal analgesic regimen, including iPACK (infiltration between the popliteal artery and posterior capsule of the knee) block, periarticular infiltration (PAI), and oral pain medications. The primary outcome was opioid consumption during the 24–48 hour postoperative period. Post-anesthesia care unit (PACU) opioid consumption was the single prespecified secondary outcome registered at ClinicalTrials.gov; all other outcomes were pre-planned exploratory analyses prespecified in the Institutional Review Board protocol.Results There was no statistically significant difference in opioid consumption during the 24–48 hour postoperative period between the continuous infusion and single-injection groups (median (IQR) 30 (15–60) mg vs 38.8 (22.9–69.4) mg; 95% CI of the median difference −22.50 to 7.00 mg; p=0.213). For the prespecified secondary outcome, opioid consumption in the PACU also did not differ significantly between groups (22.5 (16.2–30) mg vs 15 (15–30) mg; 95% CI of the median difference 0.00 to 13.50 mg; p=0.081). Catheter-associated buckling occurred in 7% of the continuous infusion group versus 0% in the single-injection group; all events were transient. No statistically significant differences were observed in patient satisfaction, length of hospital stay, or functional recovery.Conclusions Continuous adductor canal catheter infusion, initiated at the resolution of spinal anesthesia, did not reduce opioid consumption in the 24–48 hour postoperative period following primary TKA within a comprehensive multimodal analgesic regimen including perineural dexamethasone, iPACK block, PAI, oral pain medications, and continuous telemedicine-based pain consultation.Trial registration number NCT03747146.