Reliability of the Thomas test for assessing range of motion about the hip

Abstract 

Objectives

Rehabilitative protocols and research are significantly influenced by the ability to perform reliable measures of specific physical attributes or functions. The hypothesis was that the Thomas test for evaluating range of motion about the hip joint is a reliable clinical assessment tool.

Subjects

Participants (n=54) were between the ages of 18 and 45, and had no history of trauma.

Methods

Three Board-Certified Athletic Therapists assessed hip range of motion using pass/fail and goniometer scoring systems. A re-test session was completed seven to ten days later.

Results

Statistically, Kappa values for pass/fail scoring (intra-rater ℜ=0.47, inter-rater ℜ=0.39) and ICC values (intra-rater ℜ=0.52, inter-rater ℜ=0.60) for goniometer data both indicated that the Thomas test demonstrated poor intra and inter-rater reliability. However, measurement error values (SEM=1°, ME=2°, and CV=15%) and Bland and Altman plots demonstrated that there was only a small degree of intra-rater variance for each examiner when executing the Thomas test in a clinical setting.

Conclusions

Results call into question the statistical reliability of the Thomas test, but provide clinicians with important information regarding the reliability limits of the Thomas test when used to clinically evaluate hip range of motion and ilio-psoas muscle flexibility in a physically active population. More research is required in order to determine the variables that may confound statistical reliability of this orthopaedic technique that is commonly used in a clinical setting to assess hip function.

Keywords: Special tests, Orthopaedic evaluation, Flexibility measurement