Relationship Between Pedometer-Based Physical Activity and Physical Function in Patients With Osteoarthritis of the Knee: A Cross-Sectional Study

Objective: To examine the association between pedometer-based ambulatory physical activity (PA) and physical function in patients with knee osteoarthritis (OA). Design: Cross-sectional observational study. Setting: Institutional practice. Participants: Participants in orthopedic clinics (N=207; age, 56-90y; 71.5% women) with diagnosed radiographic knee OA (Kellgren/ Lawrence [K/L] grade >= 1). Interventions: Not applicable. Main Outcome Measures: Ambulatory PA was objectively measured as steps per day. Physical function was assessed using the Japanese Knee Osteoarthritis Measure (JKOM) functional subcategory, 10-m walk, Timed Up and Go (TUG), and 5-repetition chair stand (5CS) tests. Results: Patients walking <2500 steps/d had a low level of physical function with a slower gait speed, longer TUG time, and worse JKOM functional score compared with those who walk 2500 to 4999, 5000 to 7499, and >= 7500 steps/d adjusted for age, sex, body mass index [BMI], and K/L grade. Ordinal logistic regression analysis revealed that steps per day (continuous) was associated with better physical function adjusted for age, sex, BMI, and K/L grade. These relationships were still robust in sensitivity analyses that included patients with K/L grades >= 2 (n=140). Conclusions: Although increased ambulatory PA had a positive relationship with better physical function, walking <2500 steps/d may be a simple indicator for a decrease in physical function in patients with knee OA among standard PA categories. Our findings might be a basis for counseling patients with knee OA about their ambulatory PA and for developing better strategies for improving physical function in sedentary patients with knee OA. (C) 2017 by the American Congress of Rehabilitation Medicine