What does Gillet's test assess in relation to the pelvis and sacrum?

Gillet's test is specifically designed to evaluate the movement of the ilium relative to the sacrum, particularly focusing on posterior movement. During the test, the clinician checks for any asymmetry or limitations in the pelvic mechanics when the patient flexes a hip while standing. A normal response would be observed as the ilium moves posteriorly in relation to the sacrum during hip flexion, indicating that the sacroiliac joint is functioning properly.

In cases where there is a restriction or dysfunction, the ilium may not move adequately in a posterior direction relative to the sacrum, which can suggest issues with the sacroiliac joint, such as hypomobility or pain syndromes. This test is beneficial for identifying potential sources of lower back pain or pelvic dysfunction that may arise from the sacroiliac joint. Thus, option B accurately captures the purpose of Gillet's test by emphasizing the posterior movement of the ilium in relation to the sacrum.