Sixty-one patients with knee osteoarthritis were randomized to receive an open-label placebo with verbal suggestions indicating pain relief (n=21) or mood improvement (n=21), or no treatment (n=19). The primary outcomes of interest included knee pain and function (Numeric Rating Scale [NRS]; Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]). Secondary outcomes of interest included course of pain and mood ratings, need for analgesics, global clinical improvement, quality of life, perceived stress, salivary cortisol, and heart rate variation. Outcomes were assessed after 21 days of intervention. Results revealed patients who received an open-label placebo had significantly lower NRS and WOMAC pain scores, as well as a greater perceived clinical improvement vs. no treatment.