Discordance Between Self-Reported And Performance-Based Physical Function In Patients With Knee Osteoarthritis: Associations With Pain Intensity And Negative Affect

Purpose: Functional limitations in patients with painful knee osteoarthritis (OA) are evaluated clinically with self-reported measures (SRM) and performance-based measures (PPM) of physical function. Recent findings from an expert survey have shown that high self-reported functional limitations - measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical functional subscale - are a strong indication criterion for total knee arthroplasty (TKA). However, given the poor-to-moderate correlation between SRM and PPM, some patients may report having high self-reported functional limitation without the concomitant severe limitations in observed functional performance. Potentially, a substantial overestimation of perceived over observed physical disability could (i) perpetuate further disability from an underutilization of one’s physical potential, and (ii) result in unnecessary TKA or post-TKA dissatisfaction. While the concept of SRM-PPM discordance and its association with negative affect have been explored in gerontological literature, contributors to this discordance are relatively unexplored in the OA population. Thus, this study aimed to examine, in patients with knee OA, whether pain intensity and symptoms of anxiety and depression were associated with discordance of WOMAC with PPM of physical function. Specifically, we examined the PPMs of walking and stair climbing given previous reports that painful knee OA affects these functional activities more than any other diseases.