Three-dimensional Motion Analysis of Sacroiliac Joint Mobility: A Reliability Study

Background: Sacroiliac joint (SIJ) movement has been investigated in many studies using a motion analysis system; however, the reliability of this method has not been well defined yet. Objectives: This study aimed to investigate the reliability of measuring the three-dimensional (3D) movement of the SIJ through the motion analysis system. Methods: A total of 10 healthy participants performed three forward flexions from a standing position twice in one session with an interval of 30 minutes. The movements were captured by the VICON motion analysis system, and the motion of the sacrum relative to each innominate was estimated in three plans of movement. The test-retest reliability was calculated with the average of three trials using the intraclass correlation coefficient (ICC) with a 95% confidence interval (CI). Results: The measurements demonstrated good to excellent reliability (ICC: from 0.61 to 0.97) that was achieved for the SIJ motion variables. Conclusion: The outcomes of this study showed that the 3D motion analysis can be used for the evaluation of SIJ mobility due to its acceptable reliability.