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A Radiostereometric Analysis of Movements of the Sacroiliac Joints During the Standing Hip Flexion Test

Sturesson, Bengt MD*; Uden, Alf MD, PhD†; Vleeming, Andry PhD‡


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.

Sacroiliac joint (SIJ) mobility continues to be a major issue for debate. 1,2,4,28 Postmortem analysis has shown that up to an advanced age, small movements are measurable under different load conditions. 11,22,25 Reliable studies on living persons have been performed with radiostereometric analysis (RSA) of implanted markers, 3,19–21 and with measurements based on implanted external Steinman rods. 7,8

Various clinical motion tests have been proposed for the study of normal and impaired motion of the SIJ 5,6 but no thorough evaluation is available to clarify whether a motion test can specifically identify SIJ displacements.

The standing hip flexion test (SHFT) (also called the Gillet’s test or “rücklauf” test) has been used frequently to analyze SIJ mobility. The SHFT is performed with the subject in a standing position. The posterior superior iliac spine is palpated with one thumb placed on it caudally and the other thumb placed at the S2 tubercle on the sacrum. The patient then maximally flexes the hip and knee on the tested side. If the movement is normal, it is assumed that the posterior superior iliac spine moves downward, but if the joint is “blocked,” it moves upward in relation to the other side. 6,12

Potter and Rothstein 12 reported 47% agreement in an intertester reliability study of the SHFT test, and McCombe et al 10 reported a kappa value of 0.4 in a reproducibility study of physical signs in low back pain. Landis and Koch 9 stated that kappa values greater than 0.4 indicate a moderate strength of observer agreement. However, even a moderate level of agreement does not prove that the SHFT does in fact demonstrate movement in the SIJ.

The goal of the current study was to test the hypothesis that increased load significantly reduces the movements of the SIJ according to the theory of form and force closure proposed by Snijders et al. 16 This theory implies that increased axial load and the effect of the muscles will force the surfaces of the SIJ closer together, thereby increasing the fitting. The forces of friction also will be increased by the counteracting transversely oriented muscles such as the oblique and transverse abdominal, gluteus maximus, coccygeus, and piriformis muscles, 17 which also reduce the movement of the SIJ on the unloaded side.

The current study addressed the following questions: Which movements occur in the SIJ when patients alternately and maximally flex the left and right hips? Do both ilia move as a unit around the sacrum, or can provocation of one side cause the left and right SIJs to move in different directions? Is it possible to use the SHFT as a clinical diagnostic test?

From the *Department of Orthopaedics, NVS Ängelholm, Sweden, the †Department of Orthopaedics, Malmö University Hospital, Lund University, Lund, Sweden, and the ‡Spine and Joint Centre Rotterdam and Research Group Musculoskeletal System, Department of Anatomy, Erasmus University Rotterdam, The Netherlands.

Acknowledgment date: November 4, 1998.

First revision date: February 15, 1999.

Acceptance date: April 22, 1999.

Address reprint requests to

Bengt Sturesson, MD

Department of Orthopaedics

Ängelholm Hospital

S-262 81 Ängelholm


Device status category: 1.

© 2000 Lippincott Williams & Wilkins, Inc.