Reliability of the modified Thomas test in those with low back pain

Low back pain (LBP) is a leading global health concern, contributing to disability and healthcare costs. The Modified Thomas Test (MTT) is a commonly clinical measure of hip flexor length, which may be associated with LBP. However, limited research has evaluated its reliability in populations with LBP, particularly with considerations for pelvic tilt control and examiner experience.

Given the high prevalence of LBP, reliable assessment tools such as the MTT are essential for evaluating contributing musculoskeletal factors. This study evaluated intra- and inter-rater reliability of the MTT in individuals with LBP, using standardized pelvic tilt control to improve measurement consistency.

Cross sectional reliability study.

Fifty-four participants (mean age 28.67 ± 12.45 years) with LBP (mean Modified Oswestry Disability Index [MODI] 21.2 %, SD 16.38, range 0-68 %) underwent MTT assessments. Measurements were taken bilaterally, resulting in 108 total observations. Two examiners each conducted two blinded trials per limb, ensuring neutral pelvic positioning via palpation. Intraclass Correlation Coefficients (ICCs) and Standard Errors of Measurement (SEMs) were calculated using SPSS.

Intra-rater reliability was good to excellent (ICC = 0.89; range: 0.858-0.906). Inter-rater reliability was strong (ICC = 0.86; range: 0.819-0.890). Participants reported low to moderate disability levels (MODI = 21 % ± 16.38; Roland-Morris Disability Questionnaire [RMDQ] = 5 % ± 5.67).

The MTT demonstrated good-to-excellent intra- and inter-rater reliability in individuals with LBP when pelvic tilt was standardized. These results support its use as a reliable method for assessing hip flexor length in individuals with LBP, though further research is needed to confirm reliability in populations with higher pain and disability levels.