Two hundred and thirty patients with knee osteoarthritis and scheduled for a primary non-drainage total knee arthroplasty (TKA) using combined spinal epidural anesthesia with a short-acting opioid were randomized to receive indwelling urinary catheterization for up to 24 hours post-operation (n=115) or no urinary catheterization (n=115). The primary outcome of interest was the incidence of post-operative urinary retention. Secondary outcomes of interest included knee flexion and extension range of motion, the Knee Society Score (KSS) Knee and Functional Scores, the incidence of urinary tract infection (UTI), intra-operative intravenous fluid, operative time, whole blood loss, hemoglobin (g/dL) and hematocrit (%) drop, and length of hospital stay. Range of motion and KSS scores were assessed at 3 and 6 months post-operation. Results revealed no statistical significant differences between the urinary catheterization group and control group in all outcomes (p>0.05 for all).