THOMAS TEST FOR ILIOPSOAS LENGTH The Thomas Test is a great quick test to assess the length of your patients hip flexors. If the the extended leg does not remain on the treatment bench during contralateral hip flexion, this is a sign of a shortened iliopsoas muscle. Peeler et al. (2007) have evaluated the test's reliability and found an intra-rater reliability of 0.47 and an inter-rater reliability of 0.52 for the visual method. Using a goniometer yielded slightly better results. Nonetheless, th