Addition of aerobic physical activity to resistance exercise for hip osteoarthritis (PHOENIX): a randomised comparative effectiveness trial

Abstract

Background: Exercise is recommended for hip osteoarthritis, but the most effective programmes for management of symptoms are unknown. We aimed to investigate whether adding aerobic physical activity to resistance exercise would improve hip pain and function more than resistance exercise alone in individuals with hip osteoarthritis.

Methods: PHOENIX was a randomised comparative effectiveness trial done in Melbourne, Australia. We recruited people with a clinical diagnosis of symptomatic hip osteoarthritis. Participants were randomly assigned (1:1, by use of a web-based system) to aerobic physical activity and resistance exercise or resistance exercise only. Both groups received a home exercise programme and nine consultations with a physiotherapist over 3 months. The co-primary outcomes were change in hip pain severity (numerical rating scale [NRS] 0-10, with higher scores indicating worse outcomes) and function (Western Ontario and McMaster Osteoarthritis Index [WOMAC]; scale 0-68, with higher scores indicating worse outcomes) at 3 months. Analyses were done in the intention-to-treat population. People with lived experience of hip osteoarthritis were involved in the design of the study. This trial is registered with the Australian New Zealand Clinical Trial Registry (ACTRN 12619001297112), and is complete.

Findings: Between Oct 15, 2019, and Sept 13, 2022, 196 participants (134 [68%] women and 62 [32%] men) were randomly assigned to aerobic physical activity and resistance exercise (n=97) or resistance exercise only (n=99). At 3 months, aerobic physical activity and resistance exercise was not more effective in improving hip pain severity (mean difference 0·3 [95% CI -0·3 to 0·8; p=0·36]) or function (mean difference -0·9 [95% CI -3·6 to 1·8; p=0·51]) compared with resistance exercise alone, with both showing a mean improvement in pain (2·4 [SD 1·9] with aerobic physical activity and resistance exercise vs 2·2 [2·1] with resistance exercise only) and function (7·0 [10·4] with aerobic physical activity and resistance exercise vs 8·9 [10·8] resistance exercise only). There were 24 related adverse events with aerobic physical activity and resistance exercise, and 31 with resistance exercise only, none of which were serious.

Interpretation: Despite improvement in pain and function in both groups, adding moderate-intensity aerobic physical activity to resistance exercise did not lead to superior outcomes. Future work could consider higher intensity interval training before concluding no symptomatic benefit of adding aerobic exercise or physical activity to resistance exercise.

Funding: National Health and Medical Research Council, Australia.