INTRODUCTION: Effective analgesia after total hip arthroplasty must minimize pain and optimize early ambulation. Lumbar plexus blocks (LPBs) provide analgesia but may cause motor weakness. Quadratus lumborum blocks (QLBs) may provide analgesia with preserved motor strength. METHODS: This trial randomized subjects scheduled for elective hip arthroplasty to receive an LPB or lateral QLB for postoperative analgesia. The primary outcome was opioid consumption at 12-hour postoperative. Non-inferiority of lateral QLBs compared with LPBs was conducted using a one-sided two-sample t-test. Secondary outcomes included pain scores, cumulative opioid consumption, quadriceps strength, time to ambulation, and distance ambulated. Differences in pain scores and opioid consumption over time between groups were evaluated using a linear mixed model. RESULTS: The trial consented and randomized 111 subjects and 103 completed the study: LPB (n=50) and lateral QLB (n=53). Mean (95% CI) cumulative opioid consumption (mg) at 12-hour postoperative was not found to be non-inferior in the lateral QLB (15.9 (12.7 to 19.2)) vs the LPB (12.7 (10.2 to 15.1)) group (p=0.625). Pain scores in postoperative anesthetic care unit (PACU) and 24-hour postoperative did not differ. The maximum distance ambulated did not differ, but lateral QLB patients were 2.4 times more likely to ambulate in the first 12 hours (p=0.024) and had significantly greater quadriceps strength in PACU (p<0.001). DISCUSSION: Although we were unable to demonstrate non-inferiority for opioid consumption at 12-hour postoperative, strength and mobilization were improved in lateral QLB subjects. TRIAL REGISTRATION NUMBER: NCT04402437.