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.