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

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.

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.

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.

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.