Intra- and Inter-rater Reliabilities of Measurements of Iliopsoas Thickness in Hip Flexion

[Purpose] To investigate the intraand inter-rater reliabilities of measurements of the iliopsoas thickness, and the change in iliopsoas thickness due to hip flexion. [Participants and Methods] The participants were 13 healthy young males. Iliopsoas thickness was measured in hip flexion of 0, 15, 30, 45 and 60 degrees at the center of the groin area using sonography. The intraand inter-rater reliabilities of measurements of iliopsoas thickness were calculated, and the iliopsoas thickness was compared among the hip flexion positions. [Results] When hip joint flexion was 45 ̊ or less, both the intraand inter-rater reliabilities of measurements of the iliopsoas thickness were high. Systematic bias was not found at any of the hip flexion angles. The iliopsoas thickness increased with hip flexion. [Conclusion] Highly reproducible data can be obtained by measuring iliopsoas thickness at hip flexion of 45 ̊ or less. However, as the thickness of the iliopsoas thickness changes with hip flexion, making it necessary to consider the hip flexion angle when measuring it.