Modeling Relationships among Pain and Function in Individuals with Knee Osteoarthritis in the A2CPS Cohort

OBJECTIVES: Individuals with knee osteoarthritis (OA) experience both pain and functional limitations which negatively impact quality of life and contribute to years lived with disability. Movement-evoked pain (MEP) is thought to act as a barrier to participation in daily activities, resulting in reduced function. The aim of this study was to examine the relationships between knee-specific measures of self-report pain interference, fear avoidance and performance-based MEP, and their associations with physical function among individuals with knee OA seeking joint arthroplasty. METHODS: Using baseline data from the Acute to Chronic Pain Signatures Consortium (training data: release 1.0.0, n=603; validation data: release 2.0.0, n=441), this cross-sectional study employed structural equation modeling to examine associations among self-reported pain, movement-evoked pain, and physical function. We further evaluated whether these relationships differed by task specificity and biological sex. RESULTS: Greater self-reported knee pain interference and higher fear avoidance were associated with poorer physical function (β=-0.83, P<0.001). In contrast to expectations, MEP showed little association with physical function (β=-0.11, P=0.072) and was weakly associated with self-report knee pain interference and fear avoidance (β=0.36, P<0.001). These patterns were consistent in a validation dataset. DISCUSSION: These findings suggest knee-specific self-report measures (pain, pain interference, fear avoidance) and performance-based MEP are unique constructs. Self-report measures of knee pain interference and fear avoidance were more strongly related to the functional limitations in knee OA compared to performance-based MEP.