TMS-guided physiotherapy reduces pain and induces plasticity in the motor cortex in chronic knee osteoarthritis

BACKGROUND: Knee osteoarthritis (OA) is associated with chronic pain, impaired function and loss of quality of life. Brain maladaptive plasticity may be involved and prevent beneficial effects of exercises and other interventions. Neuromodulation with peripheral electrical stimulation guided by TMS mapping may specifically influence those maladaptive modifications. OBJECTIVE: To compare the cortical organization and excitability of three muscles (straight femuris, vastus lateralis and vastus medialis) in a subject with OA knee. METHODS: This single case ABA study involved a 66 yo woman with knee OA that was considering an arthroplasty. She was assessed for pain (VAS), function (WOMAC, ICOAP), and quadriceps strength one time a week, for 10 weeks (A – four weeks assessment; B – two weeks assessment and intervention; A – four weeks assessment). TMS mapping was performed at baseline, after the two-week intervention period and at the end of the study. This examination initially revealed a prominent decrease in the volume of vastus medialis portion of the quadriceps muscle over the primary motor cortex (M1), which determined a peripheral electrical stimulation protocol specifically designed to increase this muscle’s excitability. During the intervention period the participant also carried over specific exercises daily. RESULTS: WOMAC scores, and quadriceps strength were not changed during the study period. Improvements were seen in the three subscales of the ICOAP following the intervention. This clinical change was associated with an increase in vastus medialis and also Vastus lateralis, and a decrease in rectus femuris TMS map volumes, which were maintained until the last evaluation. CONCLUSION: TMS mapping may guide specific interventions to counteract motor cortex maladaptive plasticity and positively influence pain and function in knee OA