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Introduction: Low back pain (LBP) is the most prevalent musculoskeletal condition and a leading contributor to the global disability burden. LBP remains a significant occupational health issue in Australia and other nations, accounting for a substantial portion of work-related disabilities. Early physical therapy for workers reporting LBP may reduce disability and facilitate rapid return to work. However, the lack of clearly defined guidelines for optimum timing of commencement and contextual variations, including the healthcare funding model, may influence the time to initiation of physical therapy. This study aimed to investigate the relationship between the timing of physical therapy commencement and the duration of work disability following compensable LBP onset.

Methods: This was a retrospective cohort study. We included accepted workers’ compensation claims for LBP in two Australian states. Workers injured from 2011 to 2015, aged 15–80 years and who were off work for at least two weeks were included. The primary outcome was work disability duration measured in calendar weeks, while the key independent variable was the time to initiation of physical therapy post claim onset, grouped into 0–7 days, 8–14 days, 15–30 days, > 30 days and no PT after injury. We used an accelerated failure time (AFT) model with a lognormal distribution for adjusting covariates. To determine associations between the time to initiation of physical therapy and the duration of work disability, we used time ratio estimates (TR). Associations were considered statistically significant if the TR estimates were p < 0.05. Analyses were performed in STATA 17.

Results: Our sample included 9160 accepted workers’ compensation claims for LBP. Workers who had not seen a physical therapist had the shortest duration of disability (median, 4.1 weeks). In those who had seen a physical therapist, the median duration of work disability was positively associated with the time to commencement of physical therapy. Where therapy commenced within 7 days of injury, the median duration was 8.0 weeks. Where therapy commenced more than 30 days after injury, the median duration was 34.7 weeks. Our adjusted model demonstrated that, compared to physical therapy within 7 days of injury onset, commencing physical therapy between 8 and 14 days, 15 and 30 days, and greater than 30 days was associated with a 1.37 times (Time ratios (TR) 1.37; 95 % CI (1.23, 1.52)), 2.19 times (TR 2.19; 95 % CI (1.96, 2.44)) and 4.51 times (TR 4.51; 95 % CI (4.06, 5.02)) greater likelihood of longer disability duration, respectively.

Conclusion: In workers with work-related LBP undertaking physical therapy, early commencement of physical therapy was associated with a significantly shorter duration of disability. Although we cannot establish causality, our results indicate that programs facilitating the prompt commencement of treatment may contribute to a reduction in extended work incapacity among injured workers undergoing physical therapy for LBP.