Pain sensitization as a potentially modifiable factor in people with knee osteoarthritis: insights from behavioral graded activity.

Introduction: Exercise is a first-line treatment for knee osteoarthritis (KOA); however, a substantial proportion of patients show a limited response to standardized exercise programs. Pain sensitization is increasingly recognized as a contributor to poor outcomes. This study examined changes in pain, disability, and pain sensitization after a behavioral graded activity (BGA) program in people with KOA who had not responded to guideline-concordant exercise. Methods: In this single-arm trial, the pain and activities of daily living subscales of the Knee injury and Osteoarthritis Outcome Score (KOOS) were assessed after a 12-week BGA program. Secondary outcomes included pressure pain threshold (PPT), temporal summation of pain (TSP), and step count. Baseline radiography and magnetic resonance imaging (MRI) were used to characterize structural abnormalities as potential effect modifiers. Results: Twenty-six participants completed the intervention. Linear mixed models showed significant improvements in KOOS pain and activities of daily living, exceeding the minimal important change. PPT increased at both the knee and forearm, TSP decreased, and physical activity increased. Baseline step count was positively correlated with improvement in KOOS activities of daily living, whereas structural abnormalities and pain sensitization measures were not associated with changes in KOOS outcomes. Discussion: Clinically meaningful improvements in KOOS were accompanied by concurrent changes in PPT and TSP over the 12-week BGA program in people with KOA who had not responded to guideline-concordant exercise. Future randomized controlled trials are needed to determine whether these sensory changes are attributable to BGA and to identify patient characteristics associated with treatment response.