Kendall / Modified Thomas Test for Rectus Femoris Length The modified Thomas test is probably the most commonly used test to measure any hip extension defitits due to muscle shortening. But how reliable and valid is this test? Peeler et al. (2013) showed an almost perfect intra- and inter-rater reliability for the visual and goniometer methods (0.92-0.98). Vigotsky et al. (2016) evaluate the criterion reference validity of the Thomas test to measure peak hip extension and hip extension deficits.

HIP ASSESSMENT SERIES PART 13: THOMAS TEST FOR ILIOPSOAS TIGHTNESS Hip flexion can be impaired not only to a tight rectus femoris muscle but more often than not due to tightness of the iliopsoas muscle. The Thomas test is the most common quick test to assess for contractures or tightness of this muscle that runs from the lateral part of the segments T12-L4 and the iliac fossa to the lesser trochanter. | Physiotutors

Hip Flexor strength testing - iliopsoas & rectus femoris - break test