Adherence to exercise among people with knee osteoarthritis

Abstract

Knee osteoarthritis (OA) is a significant cause of pain and disability among older adults worldwide. Evidence and all guidelines recommend exercise as the cornerstone of non-surgical treatment for all people with knee OA. However, the clinical benefits of exercise among people with knee OA have been demonstrated to be modest, and decline from short- to long-term. Poor adherence to exercise programs as prescribed has been suggested as an important factor impacting the effectiveness of these exercise interventions for people with knee OA. This thesis aimed to gain a better understanding of adherence to exercise among people with knee OA through five related studies.

Study One examined the presence of common trajectories of self-reported adherence to home exercise programs over time among a large cohort of people with knee OA. Using latent class growth analysis three distinct trajectory groups were identified: a “Rapidly declining adherence” group, a “Gradually declining adherence” group and a “Poor adherence” group. These findings affirmed the importance of monitoring adherence, and identifying interventions and behaviour change techniques to achieve and maintain adherence to exercise long-term.

Study Two clarifies the current understanding of interventions targeting adherence to exercise among older adults with knee/hip OA or chronic low back pain by way of a systematic review. Meta-analysis found moderate quality evidence that booster sessions with a physiotherapist may improve exercise adherence in people with lower limb OA. Findings highlighted the limited number and heterogeneous nature of published randomised controlled trials (RCTs) specifically evaluating interventions aimed at increasing exercise adherence. Study Three explored the perspectives of people with knee OA and physiotherapists who treat people with knee OA regarding theory-derived behaviour change techniques (BCTs) to improve adherence to exercise. Results of the online questionnaire identified a mismatch between the BCTs experienced by people with knee OA and used by physiotherapists, and those perceived to be most likely to be effective.

A limitation identified in Studies One, Two and Three was the lack of evaluation of the validity and reliability of commonly used self-reported measures of exercise adherence. Study Four used unique concealed accelerometer technology to examine the concurrent validity of exercise diary completion and a retrospective self-rated adherence scale among a cohort of older adults with chronic knee pain undertaking a home strengthening program. Both self-reported measures showed questionable validity, and the self-rated adherence scale also demonstrated less than acceptable test-retest reliability. Finally, using the accelerometer-measured exercise adherence data Study Five examined the effect of home exercise adherence on changes in patient outcomes of pain, function and quadriceps strength over the 12-week intervention. While a significant decline in adherence, and significant improvements in patient outcomes were observed, the level of home exercise adherence was not significantly associated with changes in these outcomes in linear or non-linear models.

Taken together, the findings of these studies provide new knowledge of adherence to exercise specifically among people with knee OA. Furthermore, the results of this work raise a number of research questions worthy of future investigation.