The influence of pelvic rotation on clinical measurements of hip flexion and extension range of motion across sex and age

Abstract

ObjectiveThe purpose of this study was to identify the amount of pelvic rotation associated with hip motion during passive hip flexion and extension goniometric measurements. DesignCross-sectional study. SettingUniversity laboratory. ParticipantsOne hundred healthy adults (males = 45, females = 55) aged 18–66 years participated. Outcome measuresClinical range of motion measurements of hip flexion, and extension during the modified Thomas test, and pelvic sagittal position measured using a device, attached from the PSIS to ASIS, and a fluid-filled inclinometer. ResultsWhen pelvic rotation was subtracted from the clinical measurements, hip flexion measurements were significantly reduced in both sexes (males: 110.8 ± 7.4 to 93.8 ± 7.8°, P < 0.001; females: 121.3 ± 7.2 to 107.3 ± 8.6°, P < 0.001). However, subtracting pelvic rotation from hip extension measurements only significantly reduced the measurements in females (15.5 ± 6.0 to 6.2 ± 6.8°, P < 0.001). No significant differences were found across age groups. ConclusionsClinical measurements of hip flexion exaggerated the range of motion in both sexes. The modified Thomas test appeared to control for rotation of the pelvis during hip extension in men. However, in women, hip extension measurements were exaggerated.