Who participates in randomised controlled trials evaluating physiotherapy interventions for persistent low back pain? A scoping review

Background: Low back pain (LBP) disproportionately affects socioeconomically disadvantaged individuals, minority ethnic communities, and those with multiple long-term health conditions; groups often under-represented in research studies. This scoping review aims to establish who participates in randomised controlled trials (RCTs) evaluating physiotherapy interventions for persistent LBP. Methods: The review protocol was registered (https://doi.org/10.17605/OSF.IO/Y9CR4). Six databases were searched between January 2020 and June 2024. Eligible studies were RCTs of physiotherapy interventions for adults (18+) with persistent LBP. RCTs could be conducted in any setting and published in English. Data were analysed descriptively. Results: 108 RCTs were eligible. Most RCTs did not report on key participant characteristics, such as ethnicity (n = 103, 95%) or comorbidities (n = 100, 93%). Where reported, mean age was 42.3 years (±9.6), 50.8% (±23.9) were female and 72.4% (±8.5) were from white ethnic backgrounds. Age (n = 102, 94%) and duration of LBP (n = 99, 92%) were the most common inclusion criteria. Language restrictions were the most reported participant characteristic (n = 24, 22%). The most reported reason for exclusion was previous spinal surgery (n = 74, 69%). People with mental health conditions were excluded in 30% (n = 32) of RCTs. Conclusion: Most RCTs evaluating physiotherapy interventions for LBP do not report key participant characteristics, such as ethnicity, work status and health comorbidities. Where reported, people at higher risk of persistent and disabling LBP, particularly those with mental health conditions and from ethnic minority groups, are often excluded or under-represented. Future RCTs should adopt inclusive strategies to better reflect the populations most affected by LBP.