Changes in prefrontal cortex activation with exercise in knee osteoarthritis patients with chronic pain: An fNIRS study

The role of exercise on pain modulatory mechanism of the prefrontal areas is not clear. We aimed to determine the effects of exercise on functional activity of the prefrontal cortex in patients with knee osteoarthritis (OA) with chronic pain and to assess the relationships between changes in clinical variables and cortical hemodynamics with exercise via functional near-infrared spectroscopy (fNIRS). Fifteen patients with knee OA with chronic pain were included. All participants attended an exercise program 3 times a week for 6 weeks. Pain during activity was assessed by visual analogue scale (VAS). Pain catas-trophization, kinesiophobia and functionality were also measured. Brain hemodynamic activity was assessed with a 47-channel fNIRS system before and after the exercise. Pain, pain catastrophization, kine-siophobia and functionality scores significantly improved (p < 0.05) while functional activity of the dor-solateral prefrontal cortex (DLPFC) during painful stimuli was significantly reduced after exercise program (p < 0.05). Change in cortical hemodynamic activity within the DLPFC was significantly corre-lated with change in pain perception (R = 0.54, p < 0.05) and pain catastrophization scores (R = 0.44, p < 0.05). Exercise resulted in improvements in clinical assessments of pain severity and pain catastro-phization which was accompanied by alterations in prefrontal cortex activation. We provided evidence about the pain modulatory effects of exercise at cortical level which is correlated with clinical improve-ments in patients with chronic pain. We demonstrate the feasibility and potential of fNIRS methodology for i) elucidating the neural mechanisms underlying chronic and stimulus evoked pain, and ii) exploring the effect of treatment methods on brain functionality. (c) 2021 Elsevier Ltd. All rights reserved.