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1995 Publications

Pelvic Tilt Detection During the Thomas Testby Tyler T, Henline D, Ferriter P, Gleim GWNicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, NY - last modified 2013-02-09 00:00
JOSPT 21(1), January 1995.


The Thomas test was designed as a clinical test for identifying iliopsoas contracture. Pelvic stabilization is necessary in order to accurately quantify hip extension range of motion (ROM). We addressed the problem of pelvic stabilization by developing an electrical circuit for detecting anterior pelvic tilt detection. In order to validate the device, we obtained X-ray pictures of the lumbar spine and pelvis while employing the device during the Thomas test.

The test leg in six subjects was braced in knee extension, and hip extension ROM was measured goniometrically, using the Thomas test position. An electrode placed on the L4-L5 vertebral interspace illuminated a light when it came into contact with the X-ray table. X-ray and ROM measurements were taken simultaneously at the point of maximum hip extension with the light on. Posterior pelvic tilt, indicated with the light on, is the proper position of the pelvis for the Thomas test.

A second measurement was taken at the point where contact was broken and the light was off. Lumbosacral joint angle was calculated from the X-rays and hip extension ROM was measured and analyzed using a t-statistic. With the light on, the mean hip extension ROM was 7.5 deg. and the pelvic tilt angle was 20.7 deg. These values corresponded to -2.8 deg. for hip ROM and 31.8 deg. for pelvic tilt with the light off.

Both measurements proved to be highly significant when comparing the measurement with the light on to the one with the light off (p < .001). As pelvic tilt increased, the goniometric measurement of hip extension ROM increased. Consequently, the device was able to detect pelvic motion as documented by X-ray. Knowledge of proper pelvic positioning while administering the Thomas test should increase measurement accuracy.