Pain in Individuals With Knee Osteoarthritis : Beyond the Joint and the Musculoskeletal System

Introduction: Total knee arthroplasty (TKA) is an effective intervention to relieve people with osteoarthritis (OA). Nevertheless, 15 to 30% of patients continue to experience severe pain following surgery. Recent data suggest that central nervous system (CNS) changes may play a role in OA pain and possibly explain why some patients have poorer clinical outcomes following TKA. Objectives: Our main objectives are to explore the relationship between OA pain and (1) the integrity of corticospinal system, (2) the efficacy of descending pain inhibition circuits. Methods: Fifty-two patients waiting for TKA will be recruited. The integrity of the corticospinal projections will be measured using transcranial magnetic stimulation (recruitment curve of the affected quadriceps femoris muscle) and the descending pain inhibition circuits (bulbospinal projections) will be assessed by a counter-irritation paradigm (i.e., conditioned pain modulation with immersion of the arm in painfully cold water). Diffuse tension imaging (DTI) will also be used to quantify the strength of these corticospinal and bulbospinal projections. Clinical outcomes will be evaluated before and after arthroplasty with a series of validated questionnaires such as the WOMAC Scale, the McGill Pain Questionnaire and the Brief Pain Inventory. These different neurophysiological and clinical measures will be taken before surgery, 6 months after surgery and 1 year post-surgery. Anticipated results: The investigators expect a moderate association between pain and the strength of the corticospinal and bulbospinal projections. Moreover, it is expected that there will be a moderate association between the strength of the corticospinal/bulbospinal projections and the clinical evolution of patients.