Changes in physical activity and the association between pain and physical activity - a longitudinal analysis of 17,454 patients with knee or hip osteoarthritis from the GLA:D® registry

OBJECTIVE: Investigate change in physical activity following an 8-week education and exercise therapy program for patients with knee/hip osteoarthritis, focusing on those with low physical activity level. Furthermore, to evaluate associations between changes in pain intensity and physical activity.

METHOD: Data from the Good Life with osteoArthritis in Denmark (GLA:D®) registry, at baseline, immediately after completion, and 12 months after entering the program was used. Measures of interest were UCLA activity scale (1-10) and Visual Analog Scale for pain intensity (0-100 mm). Changes in physical activity levels (low 1-4, moderate 5-6, and high 7-10) over three time points were investigated. Asymmetric fixed effects regression models were used to evaluate the association between clinically relevant change in pain (≥15 mm) and change in physical activity level from baseline to 12 months.

RESULTS: 37% with low activity level at baseline (n = 4,836) and 69% of all patients (n = 17,454) reached or maintained at least a moderate physical activity level at follow-ups. Surprisingly, both an improvement (β = 1.44, P < 0.001) and a worsening (β = 1.18, P < 0.001) in pain intensity was associated with increased physical activity in low activity patients. For all patients a similar trend was observed (β = 0.51, P < 0.001 and β = 0.11, P = 0.215, respectively).

CONCLUSION: In low active knee or hip OA patients, a third of patients participating in an education and exercise therapy program reached and maintained at least a moderate physical activity level for 1 year. The improvement in physical activity was not dependent on pain reduction.