A radiostereometric analysis of movements of the sacroiliac joints during the standing hip flexion test.

Study Design: The standing hip flexion test was evaluated by using a radiostereometric analysis.

Objectives: To evaluate whether the commonly used standing hip flexion test reflects movement in the sacroiliac joints, or whether the increased load of one sacroiliac joint also reduces the mobility of the other sacroiliac joint according to the theory of form and form closure in the sacroiliac joints.

Summary Of Background Data: The standing hip flexion test, used frequently to analyze sacroiliac joint mobility, is advocated as a test for study of normal or impaired motion in the sacroiliac joint.

Methods: In this study, 22 patients considered to have sacroiliac pain were analyzed with radiostereometric analysis when standing and when performing the standing hip flexion test on the right and left sides.

Results: Very small movements were registered in the sacroiliac joints. When provoking one side, the rotations were small on both sides.

Conclusions: The small movements registered support the theory of form and force closure in the sacroiliac joints. The self-locking mechanism that goes into effect when the pelvis is loaded in a one-leg standing position probably obstructs the movements in the sacroiliac joints. Therefore, the standing hip flexion test cannot be recommended as a diagnostic tool for evaluating joint motion in the sacroiliac joints.