In this study we investigated the relative effectiveness of US therapeutic acoustic radiation for patients with knee OA over 8-minute and 4-minute treatment sessions. Patients also received physical therapy sessions and transcutane- ous electrical nerve stimulation throughout the study and signi cant improvement was noted in self-ratings of pain intensity, physical functionality, and depressive symptoms. Yet, patients randomly assigned to the 8-minute US group achieved better results in their pain and ability to perform activities of daily living in comparison to patients receiving 4-minute treatments. There are con icting data regarding the ef cacy of US therapeutic acoustic radiation treatment for knee OA29–34). Speci cally, in 2010 the International Os- teoarthritis Research Society recommended that the optimal management for hip and knee OA requires a combination of non-pharmacological and pharmacological modalities including physical therapy, but does not speci cally mention US therapeutic acoustic radiation as an adjunct35). Several authors have researched the effectiveness of US therapeutic acoustic radiation treatment, but its clinical ef cacy remains controversial2, 15–20). However, our ndings indicate that US therapeutic acoustic radiation treatment may be more effec- tive in treating knee OA than previously thought. In fact a study that Ozgonenel et al.16) compared US with sham US in the treatment of knee OA revealed that US was superior to placebo, yet there were further OA treatments provided that may have obscured whether or not the effect was due to US alone.