Effects of Pulsed Ultrasound on Knee Joint Friction and Inflammation in Non-traumatic Experimental Osteoarthritis

Knee Osteoarthritis (OA) is one of the most important etiologies of pain and disability among adults. The effects of pulsed Ultrasound (US) on pain reduction and joint function have been proven, but its role on joint friction and inflammatory mediators is still unclear. Therefore, this study was designed to investigate the effects of US on knee joint friction and inflammation in non-traumatic experimental knee OA. Materials and Methods: Forty-eight guinea pigs were randomly assigned into four groups: OA+US, OA+US sham, 30 days after OA induction (OA30), and normal control (n=12 for each group). OA was induced by intra-articular injection of 3 mg/kg of Mono-Iodoacetate (MIA) in the animal’s left knee. Joint circumstance and weight of the animals were measured at baseline, before (i.e., after 30 days of MIA injection), and after US treatment. Joint friction was evaluated by a pendulum friction tester system. Cytokine levels, including Tumor Necrosis Factor (TNF)-α and Interleukin (IL)-1β, were measured by the ELISA method. The Pearson correlation coefficient was calculated to study the relationships between friction and inflammation variables. Results: Joint circumference was increased in the OA30 group. Joint friction variables, including exponential curve fitting, cycle number, and friction coefficient, were significantly better in the US group (P<0.05). TNF-α and IL-1β cytokine levels were significantly lower in the US group. A significant positive correlation was observed between joint friction indices and TNF-α and IL-1β cytokine levels (P<0.05). Conclusion: US was an effective approach for reducing joint friction and inflammation in OA30. Moreover, the relationship between knee joint friction and inflammation could help us better understand the etiology, mechanism, and treatment strategies of this disease.