2. Materials and methods
2.1. Study design and participants
This study was a double-blind randomized placebo-controlled clinical trial, with a 3-month follow-up, of 120 patients with knee OA visiting Khatam-ol-anbia Polyclinic in the city of Yazd in Iran. This study was performed in the period spanning November 2011 to May 2012.
Criteria for inclusion were age (between 50 years and 70 years) and diagnosis of OA verified by a rheumatologist according to the classification criteria of the American College of Rheumatology.18 Patients with any of the following were excluded: rheumatoid arthritis, inflammatory diseases, metabolic disorders (such as diabetes, cancer, or other serious diseases), signs or history of liver or kidney failure, treatment with oral corticosteroids within a period of 4 weeks prior to the trial, corticosteroids injection within 6 months prior to the experiment, fever > 38°C at screening, permanent consumption of ginger (生薑 shēng jiāng), allergy to ginger, unwillingness to continue the protocol, avoidance of consumption of > 20% of the ginger supplements, any serious complications, consumption of multivitamin, minerals, or other nutritional supplements, and consumption of analgesic medications.