Reliability of Goniometric Techniques for Measuring Hip Flexor Length Using the Modified Thomas Test.

Background: The modified Thomas test (MTT) is commonly used to assess the flexibility of hip musculature, including the iliopsoas, rectus femoris, and tensor fascia latae. This measurement is important to include in a comprehensive musculoskeletal examination. However, existing research shows conflicting results regarding its reliability, particularly due to variations in controlling pelvic tilt during testing, which may lead to inaccurate measurements of hip extension when quantifying the test outcomes.

Purpose/hypothesis: This study aimed to evaluate the intra- and inter-rater reliability of the Modified Thomas Test (MTT) in assessing hip flexor length using a goniometer. It was hypothesized that controlling for pelvic tilt would enhance the reliability of these measurements.

Study design: Intra- and inter-rater reliability study.

Methods: Sixty-four healthy individuals were recruited to participate in this study. The MTT was performed twice on each leg by both an experienced and a student physical therapist. Blinded goniometric measurements for hip extension range of motion (ROM) in the MTT position were taken with neutral pelvic tilt being enforced via palpation. A double-blind protocol was used where both examiners were unaware of each other's measurements and the goniometer was covered to blind the measuring therapist to the values as well. ROM values were entered into a Microsoft Excel spreadsheet and quantified using SPSS software. Statistical analysis included calculating Intraclass Correlation Coefficients (ICCs) and Standard Errors of Measurement (SEMs) using SPSS software.

Results: The study included 64 participants (mean age = 23.7 ± 4.34 years). The MTT demonstrated high intra-rater reliability (ICC = 0.911) and inter-rater reliability (ICC = 0.851). The SEMs indicated minimal variability around the mean scores. The average hip extension ROM measured was 5.43± 9.73 degrees.

Conclusion: These results suggest that the MTT is a reliable tool for assessing hip flexor length in clinical practice, particularly when pelvic tilt is controlled. These results have important implications for accurately testing orthopedic limitations that can contribute to low back, hip, and knee pain.

Level of evidence: 3.