Are pain, functional limitations and quality of life associated with objectively measured physical activity in patients with end-stage osteoarthritis of the hip or knee?

OBJECTIVES: Physical activity is promoted in patients with hip or knee osteoarthritis (OA), yet little is known about its relationship with symptoms, functional limitations and Quality of Life (QoL). We investigated if OA-associated pain, functional limitations and QoL are associated with objectively measured physical activity in patients with end-stage hip/knee OA. METHODS: Cross-sectional study including patients scheduled for primary total hip/knee arthroplasty. Patients wore an accelerometer (Activ8) with physical activity assessed over waking hours, and expressed as number of activity daily counts (ADC) per hour, %time spent on physical activity i.e. walking, cycling or running (%PA), and %time spent sedentary (%SB). Pain, functional limitations and joint-specific and general QoL were assessed with the Hip disability/Knee Injury and Osteoarthritis Outcome Score (HOOS/KOOS) and the Short Form (SF)-12. Multivariate linear regression models with the three to Z-scores transformed parameters of physical activity as dependent variables and adjusted for confounding, were conducted. RESULTS: 49 hip and 48 knee OA patients were included. In hip and knee OA patients the mean number of ADC, %PA and %SB were 18.79 ± 7.25 and 21.19 ± 6.16, 14 ± 6.4 and 15 ± 5.0, and 66 ± 10.5 and 68 ± 8.7, respectively. In hip OA, better joint-specific and general QoL were associated with more ADC, (ß 0.028; 95%CI:0.007-0.048, ß0.041; 95%CI:0.010-0.071). Also, better general QoL was associated with the %PA (ß 0.040, 95%CI:0.007-0.073). No other associations were found. CONCLUSION: Whereas QoL was associated with physical activity in hip OA, pain and functional limitations were not related to objectively measured physical activity in patients with end-stage hip or knee OA.