Sacroiliac Joint Dysfunction

Roberto Feliz

Despite the controversies, the sacroiliac joint (SIJ) has been identified as a potential cause of lower back pain since the early reports of Goldwaith and Osgood first reported it in 1905.¹ More recently, Bernard and Kirkaldy-Willis concluded that SIJ may be a primary source of pain in 22.5% of patients with lower back pain.² Other studies have reported that the true incidence of SIJ pain ranges between 15% and 23%.³

Many experts, however, believe that the pain generators in SIJ dysfunction rather include the surrounding soft tissues and stabilizing ligaments.⁴

ANATOMY AND PHYSIOLOGY

The sacrum is a wedge-shaped structure formed by five fused sacral vertebrae. The sacrum articulates superiorly with the fifth lumbar vertebra and inferiorly with the triangular-shaped coccygeal bone and laterally with the ileum. The sacrum supports the lumbar spine and helps transmit the forces from the lower extremities to the pelvis and vertebral column.⁵

The sacrum and the ileum articulate via the C-shaped synovial SIJ. This joint, surrounded by a fibrous capsule with an inner synovial lining, allows a 2 to 3 millimeter of glide and 2 to 3 degrees of rotation. Despite the limited motion across, the major function of the SIJ is to support the axial skeleton and stabilize the pelvic ring.⁶

It has been postulated that the SIJ acts as an important stress reliever in the force-motion relationships between the trunk and the lower limbs. These joints ensure that the pelvic girdle is not a solid ring of bone that could easily fracture under the great forces to which it might be subject, either from trauma or its many bipedal functions.⁷

In the adult, the SIJ has a short cranial and a longer caudal limb. The lower portion of the cranial limb and the caudal limb are synovial joints, whereas, the upper part of the cranial limb is more fibrous. The SIJ lies obliquely at an angle to the sagittal plane. In the standing position, the cranial, also known as the S1 part of the joint, lies mainly vertical, and its surface runs obliquely and sagittally from cranio-lateral to slightly cauda-medial. The surface of the SIJ is divided into three parts (cranial (S1), middle (S2) and caudal (S3)) or sacral elements. Of these, the S1 is the largest and the S3 part the smallest. The mean angle of the C-shape SIJ is 40 degrees at S1, 25 degrees at S2, and minus 10 degrees at S3.⁷

The SIJ articular surface has interdigitating symmetrical grooves and ridges. These grooves and ridges contribute to the highest coefficient of friction of any arthrodial joint. The sacrum
with its smooth keystone like bony anatomy further contributes to stability within the pelvic ring. The sacrum is wider superiorly than inferiorly; it is also wider anteriorly than posteriorly, permitting the sacrum to become “wedge” cranially and dorsally into the ilia within the pelvic ring. This anatomic structure of the sacrum in humans is adapted to resist shearing from vertical compression and anteriorly directed forces of the spine.⁷

The stability of the SIJ is partially provided by surrounding muscles and thick ligaments projecting from the spine, sacrum, and iliac bones. These include the iliolumbar, sacrospinous, interosseous, anterior and superior sacroiliac, and sacrotuberous ligament.

Anteriorly, the SIJ surface is covered by a thin anterior capsule made of a thin layer of hyaline cartilage on the sacral side and fibrocartilage on the iliac side. Posteriorly, the joint lacks a capsule coverage; however, the interosseous ligament forms the dorsal border of the joint space.

INNERVATION

Posteriorly, the SIJ is innervated by lateral branches of the posterior primary rami from L4 to S3. Anteriorly, the SIJ is innervated by lateral branches of the posterior primary rami from L2 to S2.⁸ This complex sensory innervation to the SIJ combined with anatomic variations may explain the variable referred patterns and the difficulty often encountered in diagnosis SIJ pain.⁴

CLINICAL PRESENTATION

The clinical presentation of SIJ dysfunction is pain in the lower back, buttock, and around the SIJ. One should carefully rule out disorders of the adjacent structures (i.e., lumbar intervertebral disks, facet joints, hip joints, muscles, and tendons/ligaments) as they can present with similar symptoms. Furthermore, due to the variable innervation patterns, patient may present with pain in the upper lumbar spine, the thigh region, the hip joints, and in some distal pain around the leg and feet.⁹

Disorder of the SIJ may occur after acute traumatic injury or repetitive shear and torsional forces on the SIJ. In patients with prior lumbar fusion to the sacrum, degeneration of the SIJ may occur as an adjacent segment disease.

A thorough history and complete physical examination are very important to help differentiate SIJ pathology from the mimicking differential diagnosis.

The SIJ pain tends to be worse in the morning and may be aggravated by Valsalva maneuver, truck flexion, prolong seating, or weight bearing on the affected limb. The pain improves with flexion of the affected leg and transferring weight bearing onto the non-painful leg.⁶

DIAGNOSIS

There is no definitive diagnostic test with sufficient sensitivity and specificity. However, there are numerous clinical and interventional maneuvers to help with the diagnosis.⁴,¹⁰

These tests include:

Patrick’s test, also known as Fabere sign: Fabere sign is an acronym for the position in which the patient’s hip is passively positioned for the test: Flexion, Abduction, External Rotation, and Extension.

With the patient in the supine position, the ankle of the affected extremity is placed on the contralateral knee to create a figure-4 position. The examiner places the hand along the medial aspect of the knee of the affected extremity and applies downward vertical pressure, while simultaneously providing counterpressure with the other hand on the contralateral anterior superior iliac spine. The test is considered positive for SIJ dysfunction if pain is elicited along the ipsilateral SIJ. Because this maneuver also stresses the ipsilateral hip joint, pain elicited in the ipsilateral groin may also suggest hip disorder.

Fortin’s finger test: The patient points to the area of pain with one finger. The test is considered positive if the painful point is within 1 cm of the posterior superior iliac spine.

Gaenslen’s test: With the patient lying supine, the hip and knee of the unaffected extremity are maximally flexed and the examiner passively extends the hip of the affected leg by allowing it to slowly drop off the edge of the examining table. This maximally stresses the SIJ of the affected leg by allowing the joint to proceed though maximum range of motion. This test is considered positive if the patient experiences pain across the ipsilateral SIJ.

Distraction test: The patient lies supine, and the examiner alternately presses on each anterior superior iliac spine in a posterolateral direction. The pain is considered positive if it produces pain or asymmetric movement toward the affected side.

SIJ compression test: The patient lies prone. The examiner places the palm of the hand along the SIJ or on the sacrum and makes a vertical downward thrust. The test is positive if the patient experiences pain along the ipsilateral SIJ.

Lateral compression test: The patient lies in a lateral decubitus position. The examiner applies downward pressure on the iliac crest, compressing it against the table. The finding is considered positive if the patient experiences pain across either the SIJ or pubic symphysis.

Anteroposterior pelvic compression test: Similar to the lateral compression test, this test assesses for pathology localized at any of the major joints of the pelvic ring. The patient is placed supine. The examiner applies downward pressure on the pubic symphysis. The test is considered positive if the patient reports pain across either the SIJ or the pubic symphysis.

Thigh thrust test, also known as Fade test: The patient is supine with the hip on the affected side passively flexed and adducted to midline. The examiner applies downward pressure along the long axis of the femur to move the ilium posterior. The test is positive if it produces pain in the ipsilateral leg.

Passive straight leg raising test: The patient lies supine, and the examiner grasps the patient’s heel and passively flexes the hip while keeping the knee in extension. The patient is asked to maintain the position and then slowly lowers the leg. The test is positive if the patient experiences pain in the ipsilateral leg. This test is also positive in sciatica due to lumbar disk herniation.

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