Does exercise adherence influence outcome in knee osteoarthritis? - a secondary analysis of a superiority randomized...

The benefits of exercise in patients with knee osteoarthritis are well documented, but there is a knowledge gap regarding how exercise adherence influences outcome. This is a secondary analysis of a multicenter randomized controlled trial (n = 189).

To examine associations between exercise adherence (number of treatments, exercises, repetitions, and exercise duration) and short-term clinical outcomes.

Adherence was measured by number of treatments, exercises, repetitions, and cycling duration expressed as a percentage of the prescribed dose. Pearson's correlations were calculated between adherence and outcomes: knee function (Knee Injury and Osteoarthritis Outcome Score - KOOS), eight pain visual analogue scales (VAS), and quality of life (EuroQol-5 Dimension - EQ5D). Student's t-tests assessed whether adherence was associated with achieving minimal clinically important difference (MCID).

Treatment attendance was 98% in both groups. The high-dose group showed significantly lower adherence for exercises (81% vs 95%; p = .003), repetitions (79% vs 96%; p < .001), and cycling (78% vs 97%; p < .001), resulting in lower total exercise adherence (78% vs 97%; p < .001). Adherence was very weakly to weakly correlated with outcomes (r = -.209 to .117). No significant differences in adherence were found between those reaching or not reaching MCID in function, pain, or quality of life, except for pain when unloading in the final week in the high-dose group (-24.8 vs -9.5; p = .022).

Despite lower adherence in the high-dose group, adherence showed little association with clinical outcomes. These results suggest that high adherence to high-dose exercise may not be necessary for short-term benefit, highlighting the need for further research on optimal dosage and identifying meaningful adherence components.

ClinicalTrials.gov NCT02024126. First version 2013-12-26.