Effects of Covertly Measured Home Exercise Adherence on Patient Outcomes Among Older Adults With Chronic Knee Pain

Key Points

1. Exercise adherence may not always be required for a positive effect from an exercise program.
2. This means we must consider alternative mechanisms for how exercise has a positive effect.
3. We cannot yet determine who may need to be adherent for a positive outcome to be realised from an exercise program.

BACKGROUND & OBJECTIVE

Osteoarthritis (OA) is a common and debilitating condition affecting the knee. Evidence-based guidelines recommend exercise as a front-line treatment for knee OA. Home-based exercise programs offer results equal to supervised exercise sessions, whilst also being cost effective and implementable as a long term self-management strategy.

Effect sizes from exercise studies for knee OA have been shown to be moderate. One of the proposed reasons for the moderate effect is limited patient adherence to the exercise programs (1). Research into adherence is currently sparse and the research focuses on self-reported measures, such as exercise diaries, which can be inaccurate due to errors in estimation and recording (2,3). The authors’ hypothesis for this study was that increased adherence would result in reduced pain, increased physical function and also increased knee extensor strength.

Evidence-based guidelines recommend exercise as a front-line treatment for knee OA.

We must start to recognise that there may be varying mechanisms, including non-physical ones, through which exercise may have a positive effect.

METHODS

60 participants in Melbourne, Australia were recruited with 90% (n=54) completing the study. The inclusion criteria was: (1) aged 45 years or older, (2) knee pain on most days of the past month, (3) knee pain for 3 months or longer, and (4) overall average knee pain in the last week of 4 or greater on an 11-point numeric rating scale. Participants were mainly female (n=37), and baseline pain and functional limitation was recorded as moderate.

The authors cleverly used a concealed accelerometer within an ankle weight to measure the amount of exercise performed by the participants. The ankle weight could be adjusted up to 5kg in weight and the dosage was set at 1-2 sets of 10 repetitions aiming to achieve a perceived exertion score of 4-6 out of 10 on the Borg scale. Exercise was performed on 5 self-selected days of the week.

Each participant had a session with a physical therapist at weeks 0,2,4,6,8,10,12. During these sessions the primary outcome measures were recorded online and a review of exercise technique was performed. Pain and physical function was recorded via the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index). Knee extensor strength was measured using isometric strength testing on a custom apparatus.

RESULTS

For all participants the primary outcome measures improved significantly from baseline. Baseline WOMAC pain score was 6.1 (+/- 3.3) out of 20, and at week 12 reduced to 2.9 (+/- 2.9). Baseline WOMAC function was 19.4 (+/- 9.7) out of 68 at baseline and reduced to 9.4 (+/- 9.6) at week 12. Knee extensor strength at baseline was 1.15Nm/kg (+/- 0.40) at baseline increasing to 1.49Nm/kg (+/- 0.54) at week 12. The adherence to the home exercise program declined over the 12-week study timeframe. On average 90% of the exercises were performed at weeks 0-2 compared to 65% by weeks 10-12. The variance in the amount of exercise performed also increased between weeks 0-2 to 10-12. Most importantly, adherence to the home exercise program was not statistically significantly related to changes in the primary outcome measures.

LIMITATIONS

Data collection through the accelerometer does not give information about the intensity of the exercise nor the quality of the exercise performed. These may be additional variables that influence outcomes. Baseline characteristics such as initial pain levels and physical impairments at week 0 were low in this cohort. Higher levels of pain and physical impairment may have produced greater correlations with outcomes from exercise adherence.

CLINICAL IMPLICATIONS

This paper questions the relationship between exercise adherence and desired outcomes and may explain why some patients don’t adhere well to exercise but still achieve positive outcomes. It also questions the mechanisms through which exercise may produce positive outcomes. If exercise was solely dependent on physical adaptations then adherence to the program would be required for these adaptations to occur, and we did not see this in this paper.

We must start to recognise that there may be varying mechanisms, including non-physical ones, through which exercise may have a positive effect. For some patients just interacting with a program may be enough and the psychological benefits could be the most important element. At this moment in time it is not possible to determine who may not need to be adherent to a program, and through which mechanisms each person benefits the most. This means that although the data in this paper is important, we cannot yet conclude that adherence is not important, just that it may not be required for a positive effect for all patients.

+STUDY REFERENCE

Nicolson P, Hinman R, Wrigley T, Stratford P, Bennell K (2019) Effects of Covertly Measured Home Exercise Adherence on Patient Outcomes Among Older Adults With Chronic Knee Pain. J Orthop Sports Phys Ther, 49(7), 548-556.

SUPPORTING REFERENCE

1. Marks R, Allegrante JP. Chronic osteoarthritis and adherence to exercise: a review of the literature. J Aging Phys Act. 2005
2. Jack K, McLean SM, Moffett JK, Gardiner E. Barriers to treatment adherence in physiotherapy outpatient clinics: a systematic review. Man Ther. 2010
3. Room J, Hannink E, Dawes H, et al What interventions are used to improve exercise adherence in older people and what behavioural techniques are they based on? A systematic review BMJ Open 2017