Background: Osteoarthritis is the most common arthritis that can lead to chronic pain and severe disability in patients. Researchers are looking for new treatments that are effective with fewer side effects. Curcumin is a beneficial ingredient in turmeric with anti-inflammatory properties and plays an important role in the protection of the joints against destructive factors. Gingerol and piperine are the effective ingredients of ginger and black pepper, respectively, that may lead to the reinforcement and continuation of the effect of curcumin. The aim of the present study was to determine the efficacy of turmeric, ginger, and black pepper extracts in pain and functional improvement of patients with chronic knee osteoarthritis in comparison to that reported for naproxen.