Association of Pain and Steps Per Day in Persons With Mild-to-Moderate, Symptomatic Knee Osteoarthritis: A Mixed-Effects Models Analysis of Multiple Measurements Over Three Years

Objective Pain is a consistently reported barrier to physical activity by persons with knee osteoarthritis (OA). Nonetheless, few studies of knee OA have investigated the association of pain with daily walking levels. The current study assessed the relationship of 2 distinct measures of knee pain with objectively measured physical activity in adults with knee OA. Methods This was a longitudinal, observational investigation of 59 individuals (48 women; mean +/- SD age 61.1 +/- 6.4 years, mean +/- SD body mass index 28.1 +/- 5.6 kg/m(2)) with clinical knee OA. Data were collected every 3 months for up to 3 years. Physical activity was characterized as the average steps per day taken over at least 3 days, mea-sured by accelerometry. Pain was measured using 2 patient-administered questionnaires: the pain subscale of the Knee Injury and Osteoarthritis Outcome Score (KOOS-pain) and the P4 pain scale (P4-pain). Mixed-effects models determined the association between pain and physical activity levels (over covariates) among adults with knee OA (alpha = 0.05). Results All covariates (age [beta = -3.65, P < 0.001], body mass index [beta = -3.06, P < 0.001], season [spring/fall beta = -6.91, P = 0.002; winter beta = -14.92, P < 0.001]) were predictors of physical activity. Neither the inverted KOOS-pain (beta = 0.04, P = 0.717) nor P4-pain (beta = -0.37, P = 0.264) was associated with physical activity. Conclusion Knee pain is not associated with daily walking levels in persons with mild-to-moderate, symptomatic knee OA. While pain management remains an important target of interventions, strategies to increase steps per day in this population should focus on overcoming potentially more crucial barriers to activity participation.