OBJECTIVE: As outlined in our previous study, this study aims to investigate the role of body mass index (BMI) as an effect modifier in the relationship between conditioned pain modulation (CPM) and clinical outcomes, including depression, quality of life, and pain in individuals with knee osteoarthritis (KOA). METHODS: This cross-sectional analysis is part of the DEFINE Study in Rehabilitation. A total of 113 participants with KOA, admitted to the Instituto de Medicina Física e Reabilitação (IMREA) rehabilitation program, were included. Clinical and neurophysiological assessments were conducted, focusing on CPM, the Hamilton Depression Rating Scale (HDRS), and the SF-36 health survey. BMI was stratified into two categories based on the mean BMI of 31.99 kg/m RESULTS: In participants with BMI <
31.99 kg/m CONCLUSIONS: BMI acts as an effect modifier in the relationship between CPM and clinical outcomes in individuals with KOA. Obesity appears to hinder the beneficial relationships between clinical symptoms and CPM, leading to a less favorable link between physical and emotional functioning and CPM. These findings highlight the importance of considering BMI in treatment strategies for KOA, particularly when addressing the impact of lifestyle and other modifiable factors that influence pain modulation.