Relationship of the pelvic angle to the sacral angle: measurement of clinical reliability and validity.

There is a need to better document the reliability and validity of assessment measures used in physical therapy. Studies documenting the reliability of measurement of the pelvic angle and its relationship to sacral motion are presently inconclusive. The purpose of this study was twofold. First, we wanted to determine the reliability and validity of a goniometric measurement of the pelvic angle. We also wanted to test the hypothesis that there is a relationship between the pelvic angle and the sacral angle. Intertester and intratester reliability of goniometric pelvic angle measurements of 23 healthy young adults were examined using three different raters. Radiographic measurements of the pelvic and sacral angle using two raters and goniometric measurement of the pelvic angle using a single rater were taken from 15 patients with low back pain who had been referred for X-rays. Intraclass correlation coefficients (ICCs) of intratester reliability for goniometric measurements of the pelvic angle were .93, .96, and .96. The intertester reliability was .95. The ICCs for intratester reliability for radiological measurements were .92 and .95 for the sacral angle and .98 for both measurements of the pelvic angle. Intertester reliability coefficients were .86 and .88, respectively. The Pearson correlation coefficients for the goniometric and radiological measurements of the pelvic angle were .85 and .68. A comparison of the radiological and goniometric measurements of the pelvic angle with the sacral angle demonstrated low average correlations of .43 and .58, respectively. The results indicate a high level of correlation between and within testers for goniometric measurements of the pelvic angle but only a fair correlation between goniometric and radiological measurements of the pelvic angle.(ABSTRACT TRUNCATED AT 250 WORDS)