Extracorporeal shock wave therapy improves motor dysfunction and pain originating from knee osteoarthritis in rats

Objective: Although there have been several reports on the use of extracorporeal shock wave therapy (ESWT), the efficacy of ESWT for knee osteoarthritis (OA) has not been clarified. The aim of this study is to investigate the effect of ESWT on OA in a rat knee model. Methods: The rats were divided into three groups: (1) control, (2) OA, and (3) ESWT (knee OA + shock wave therapy). Behavioral analysis consisted of measuring the duration of walking on a treadmill. The expression of calcitonin gene-related peptide (CGRP) in dorsal root ganglion (DRG) neurons innervating the knee using immunohistochemistry was examined in the three groups at their peak time point on the treadmill. Results: Walking duration was significantly extended 4, 7 and 14 days after ESWT in rats with knee OA (peak time point: 4 days), again decreasing by days 21 and 28. Immunohistochemical studies revealed that the OA group had significantly higher percentages of CGRP positive neurons in the DRG than were found in the control group. In addition, ESWT reduced the ratio of CGRP positive DRG neurons in the OA model. Conclusion: The improvement in walking ability and the reduction of CGRP positive neurons in DRG indicates that ESWT is a useful treatment for knee OA. (C) 2007 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.