42 patients were randomized to receive physical therapy with the addition of either an ultrasound intervention or a sham ultrasound intervention (placebo) to determine the effect of ultrasound therapy in the treatment of knee osteoarthritis. Changes in pain, knee function, ambulation activity, disability and psychological status were measured at the completion of a 3-week intervention program. The results indicated that both groups demonstrated significant improvements; however, there were no differences between the groups. There appears to be no beneficial effect of using ultrasound therapy in addition to conventional physical therapy for the treatment of knee osteoarthritis.