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Iliacus Test: Inter-rater and Intra-rater Reliability

1 May 2004


Background and Purpose. The iliacus test was designed to make a distinction between the psoas muscle and iliacus muscle when assessing hip flexor tightness. The initial study of the iliacus test in comparison to the Thomas test utilized one tester for both tests, and each subject was tested one time. The purpose of this study was to test the inter-rater and intra-rater reliability of the iliacus test as a follow-up to a previous study.

Methods. Subjects were obtained via convenience sampling and ranged in age from 21 to 95 years. Both hips of twenty-three people were tested to gather measurements for inter-rater statistics and eighteen of those people were retested for intra-rater results; Two student therapists were the testers, while a third noted the measurement without the tester or subject knowing the result. The test procedure was the iliacus test which utilized a goniometer with a bubble level to enhance the reliability of the measurement. The subjects who were retested were seen again in 1 to 14 days.

Results. The interclass correlation statistics, ICC (2,1) performed on the inter-rater data revealed a .64 correlation between the therapists. ICC (3,1) performed on the 36 hips that were tested two times revealed a .57 correlation for therapist one and a .78 correlation for therapist two.

Discussion and Conclusion. The inter-rater and intra-rater reliability values established for the iliacus test in this study are clinically consistent with values established for the Thomas test and indicate that the iliacus test is a clinically useful technique that can distinguish between psoas major and iliacus muscle tightness. The iliacus test can be used with the same clinical confidence as the Thomas test.


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