Trajectories of adherence to home-based exercise programs among people with knee osteoarthritis

To investigate the presence of different trajectories of self-reported adherence to home exercise programs among people with knee osteoarthritis (OA), and to compare baseline characteristics across identified groups.

Pooled analysis of data from three randomised controlled trials involving exercise interventions for people aged ≥50 years with clinical knee OA (n = 341). Exercise adherence was self-reported on an 11-point numerical rating scale (NRS; 0 = not at all-10 = completely as instructed). Latent class growth analysis was used to identify distinct trajectories of adherence, at intervals from 12 to 78 weeks from baseline. Baseline characteristics of these groups were compared using chi-squared tests, one-way analysis of variance (ANOVA) and Kruskal Wallis tests where appropriate.

Three distinct adherence trajectories were identified: a "Rapidly declining adherence" group (n = 157, 47.4%) whose adherence was 7.7 ± 1.6 (/10) at 12 weeks, declined to 4.2 ± 2.2 by 22 weeks and remained low thereafter; a "Gradually declining adherence" group (n = 153, 45.1%) whose adherence declined from 8.5 ± 1.5 to 7.8 ± 1.5 over the same period, and continued to decline slowly, and a "Low adherence" group (n = 21, 6.3%) whose adherence was 2.2 ± 1.4 at 12 weeks and remained low. At baseline the "Rapidly declining adherence" group reported significantly lower Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain (mean difference (95% Confidence Interval (CI)) -0.8 (-1.4, -0.2)) and better WOMAC function compared to the "Gradually declining adherence" group (-3.1 (-5.2, -1.1)).

Three trajectories of self-reported adherence to home exercises were found among people with knee OA. Findings highlight the need for close monitoring of adherence from initiation of a home exercise program in order to identify and intervene when low or rapidly declining adherence is identified.