What is indicated if the PSIS does not move during Gillet's test when the knee is brought to the chest?

In Gillet's test, the movement of the pelvic structures, specifically the posterior superior iliac spine (PSIS), is assessed in relation to the sacrum during hip flexion. When the knee is brought to the chest, the PSIS is expected to move inferiorly and posteriorly if normal movement is present. If the PSIS does not move, it indicates that the sacroiliac joint is not functioning properly, leading to a restriction in movement. This can suggest dysfunction in the sacroiliac joint or an overall restriction in the lumbopelvic region. Thus, a lack of movement of the PSIS during the test is an indicator of a positive test for restricted movement, signifying a problem that may require further clinical evaluation or intervention.

The other options do not align with the findings of restricted movement as indicated by the immobility of the PSIS. For instance, normal movement of the sacrum would imply the PSIS should show movement, which contradicts the present observation. A negative test for nerve involvement would not apply since the test is designed to assess joint movement rather than nerve function, and an indication of hamstring tightness would not directly relate to the specific findings in Gillet's test where the focus