Eighty-four patients with knee osteoarthritis scheduled for a primary unilateral total knee arthroplasty were randomized to receive 24 hours of continuous infusion of nefopam (n=42) or placebo (n=42). The primary outcome of interest was Visual Analog Scale (VAS) pain scores up to 48 hours post-operation. Secondary outcomes of interest included morphine consumption, adverse events, functional outcomes, sedation scores, and patient satisfaction. Other than VAS pain at rest at 6 hours post-operation, which was significantly lower in the nefopam group, no differences in pain scores were observed between the two groups in pain at rest or in motion up to 48 hours post-operation. Morphine consumption at 24-36 hours and in total was lower in the nefopam group. No differences were observed in the remaining outcomes.