Physical Activity and 4-Year Radiographic Medial Joint Space Loss in Knee Osteoarthritis: A Joint Model Analysis

We examined the association between physical activity (PA) and joint space loss (JSL) over 48 months in individuals with knee osteoarthritis to assess the role of the PA level in knee osteoarthritis progression.

We analyzed 1,806 participants from the Osteoarthritis Initiative. PA was measured with the Physical Activity Scale for the Elderly (PASE) and was categorized as low, moderate, or high. JSL was defined as a reduction in joint space width of ≥0.7 mm. Analyses were stratified by the baseline Kellgren-Lawrence (KL) grade. Cox proportional-hazards (CoxPH) and joint models assessed the association between baseline PA and changes in longitudinal PA and JSL, adjusting for covariates.

Over 48 months, 33.8% of the patients experienced JSL. In patients with KL grade 2, the moderate PA tertile was associated with a reduced JSL risk compared with low PA in both standard and marginal CoxPH analyses. However, in patients with KL grade 3, increasing PA in the continuous PASE modeling was associated with increased JSL risk (marginal CoxPH: hazard ratio [HR], 1.002 [95% confidence interval (CI), 1.001 to 1.004]), confirmed by joint models (HR, 1.083 [95% CI, 1.020 to 1.150]). The rate of change of PA over time did not significantly influence progression.

Moderate or high PA did not increase the 4-year JSL risk in patients with KL grade 2. However, higher current PA was associated with higher JSL risk in patients with KL grade 3, highlighting the need for further research on the complex impact of PA on osteoarthritis. These findings may help clinicians to identify patient subgroups who could benefit from tailored PA recommendations, informing value-based care and personalized osteoarthritis management.

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.