RESEARCH ARTICLE Open Access Effects of low-intensity pu

Full list of author information is available at the end of the articleportant factors regulating chondrocyte metabolism [1]. Excessive mechanical stimulus has been reported to des-troy articular cartilage directly and also induce other destructive factors [2]. Conversely, insufficient mechanical stimulus, such as that due to joint immobilization, has also been associated with cartilage destruction [3]. On the other hand, moderate (physiological) mechanical stimulus Low-intensity pulsed ultrasound (LIPUS) is a represen-tative therapy in the orthopedic field and is clinically used to treat fractures with nonunion and to promote bone union [7]. Application of high-intensity continuous ultrasound (1–300 W/cm2) generates considerable heat in living tissues. In contrast, LIPUS (<100 mW/cm2) has much lower intensities with nonthermogenic and non-destructive actions. Mechanical strains received in the skeleton result in the promotion of bone formation, possibly by inducing chondrocyte proliferation [8,9]. In this con-text, LIPUS has been shown to enhance the endochondra