The participants were recruited if they were: having symptoms of primary osteoarthritis of the
knee at one side or both sides based on the diagnosis of classification criteria for knee osteoarthritis from clinical symptoms of the American College of Rheumatology 27, which included knee pain related to 1) age 50 years or above 2) joint stiffness less than 30 minutes, and 3) crepitation; and being able to understand Thai.