8.3 Sacroiliac Joint & Pelvic Girdle Tests

Sacroiliac Joint & Pelvic Girdle Tests

Clinical Core: The sacroiliac joint (SIJ) presents a significant diagnostic challenge due to overlapping pain referral patterns with the lumbar spine and hip joint. In Canadian manual therapy practice, therapists rely on multi-test pain provocation clusters—most notably Laslett's cluster—to achieve diagnostic validity, while utilizing kinetic mobility tests like Gillet's test to evaluate biomechanical motion within the pelvic ring.

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1. Functional Anatomy & Biomechanics of the Sacroiliac Joint

The sacroiliac joint is a unique, weight-bearing, L-shaped or C-shaped joint that connects the axial skeleton to the pelvic girdle. Structurally, it is a bipartite joint:

• Anterior-Inferior Segment (Synovial Joint): Characterized by hyaline cartilage on the sacral articular surface and fibrocartilage on the iliac surface, encapsulated by a synovial membrane.
• Posterior-Superior Segment (Syndesmosis): Lacks a synovial cavity; comprised of dense, fibroelastic interosseous and posterior sacroiliac ligaments connecting the sacral and iliac tuberosities.

   FORM CLOSURE                            FORCE CLOSURE
   - Articular ridges and grooves           - Posterior Oblique Sling (Latissimus + Gluteus Max)
   - Keystone wedged sacral anatomy         - Longitudinal Sling (Erectors + Sacrotuberous Lig.)
   - Rigid interosseous ligaments           - Anterior Oblique Sling (Obliques + Adductors)
                 \                                /
                  +------------------------------+
                                 |
                     SACROILIAC JOINT STABILITY

Stability Mechanisms: Form Closure vs. Force Closure

Pelvic stability relies on two interdependent mechanisms (Lee & Vleeming):

1. Form Closure: The passive structural stability provided by articular shape, bony surface friction, interlocking ridges and grooves, and ligamentous integrity. The sacrum acts as a mechanical keystone wedged between the two iliac bones.
2. Force Closure: The dynamic stability generated by coordinated contraction of myofascial slings (e.g., the posterior oblique sling uniting the latissimus dorsi and contralateral gluteus maximus across the thoracolumbar fascia, and the biceps femoris-sacrotuberous ligament force couple).

Pelvic Kinematics: Nutation and Counter-Nutation

• Nutation (Sacral Flexion): The sacral base moves anteriorly and inferiorly relative to the ilium, while the coccyx moves posteriorly. This tightens the massive sacrotuberous and sacrospinous ligaments, locking the joint into its close-packed, most stable configuration during weight-bearing.
• Counter-Nutation (Sacral Extension): The sacral base moves posteriorly and superiorly, while the coccyx moves anteriorly. This loosens the sacrotuberous ligament and tightens the posterior sacroiliac ligaments, creating a loose-packed, less stable position.

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2. Clinical Prediction Rules: Laslett's SIJ Pain Provocation Cluster

Historically, clinicians attempted to diagnose sacroiliac joint dysfunction using isolated orthopedic tests. However, extensive research (Dreyfuss et al., Slipman et al.) demonstrated that individual provocative tests have poor reliability and high false-positive rates, largely because pain from the L4–S1 intervertebral discs and facet joints frequently refers to the buttock and posterior superior iliac spine (Fortin's area).

To overcome these limitations, Mark Laslett et al. (2003, 2005) studied composites of provocation tests against diagnostic SIJ injection. Two or more positive tests out of four (distraction, thigh thrust, compression, sacral thrust) gave sensitivity of about 88% and specificity of about 78%; three or more of six (adding Gaenslen's test performed on both sides) gave about 94% and 78%. Specificity rose (to roughly the high 80s) when patients whose pain centralized with repeated lumbar movements were excluded:

+---------------------------------------------------------------------------------+
|                LASLETT'S SACROILIAC PAIN PROVOCATION CLUSTER                    |
+-------------------+-------------------------------------+-----------------------+
| TEST NAME         | MECHANICAL VECTOR                   | TARGET LIGAMENTS      |
+-------------------+-------------------------------------+-----------------------+
| 1. SI Distraction | Posterolateral thrust on ASIS       | Anterior SI ligaments |
|    (Gapping)      | (supine, crossed-arm contact)       | (posterior joint com.)|
| 2. SI Compression | Inward downward vertical load       | Posterior & inter-    |
|    (Approximation)| through superior ilium (side-lying) | osseous SI ligaments  |
| 3. Thigh Thrust   | Posterior axial shear force down    | Posterior SI joint    |
|    (P4 Test)      | shaft of flexed femur (supine)      | capsule & ligaments   |
| 4. Sacral Thrust  | Anterior downward spring over mid-  | Sacroiliac syndesmosis|
|    (Springing)    | sacrum S2–S4 apex (prone)           | and pelvic ring       |
| 5. Gaenslen's     | Torsion: one hip flexed to chest,   | Anterior & posterior  |
|    Test           | other leg extended off table        | SI ligaments (shear)  |
+-------------------+-------------------------------------+-----------------------+
  KEY COMPOSITES (Laslett 2005): >=2 of 4 (tests 1-4) -> Sens ~88% | Spec ~78% | +LR ~4.0
                                 >=3 of 6 (incl. Gaenslen's both sides) -> Sens ~94% | Spec ~78%
  Excluding centralizing (discogenic) presentations improves specificity

Note on Clinical Sequencing: Laslett's suggested sequence begins with SI Distraction and Thigh Thrust. If both are positive, SIJ pain is likely and further provocation is unnecessary. Otherwise, Compression and Sacral Thrust are added; two or more positive tests of the four supports an SIJ source. If all of the provocation tests are negative, the SIJ is unlikely to be the pain source. Gaenslen's test adds little once the four-test composite has been completed.

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3. Laslett's Five Provocative Tests in Detail

1. Sacroiliac Distraction Test (Gapping Test)

• Patient Position: Supine on a flat, firm table with the legs extended and relaxed.
• Therapist Setup: The therapist stands beside the patient, crossing their arms so that the right palm rests on the patient's right anterior superior iliac spine (ASIS) and the left palm rests on the left ASIS.
• Execution: The therapist applies a gradual, firm, posterolateral and lateral downward thrust through both ASIS landmarks, effectively gapping the anterior margins of the sacroiliac joints while compressing the posterior joint surfaces.
• Positive Finding: Reproduction of the patient's familiar deep buttock or posterior pelvic pain.
• Target Tissue: Stretches the anterior sacroiliac ligaments; compresses the posterior articular surfaces.

2. Sacroiliac Compression Test (Approximation Test)

• Patient Position: Side-lying facing the therapist, with hips and knees flexed to 45° to 90° and a supportive pillow placed between the knees to maintain neutral hip adduction.
• Therapist Setup: The therapist stands behind the patient, placing both hands with open palms over the uppermost, lateral aspect of the superior iliac crest.
• Execution: The therapist applies a sustained, downward vertical compressive force directly toward the table through the ilium for up to 30 seconds.
• Positive Finding: Reproduction of the patient's familiar posterior SIJ or buttock pain.
• Target Tissue: Gaps the posterior joint margin and selectively stretches the posterior sacroiliac ligament complex (long and short posterior SI ligaments) and interosseous sacroiliac ligaments.

3. Thigh Thrust Test (Posterior Shear / P4 Test)

• Patient Position: Supine on the table.
• Therapist Setup: The therapist stands on the symptomatic side. The patient's hip is flexed to 90° with slight adduction, and the knee is fully flexed. The therapist slides one hand beneath the patient's sacrum to act as a firm, immovable base.
• Execution: The therapist wraps their other hand and forearm around the patient's flexed knee, aligning their forearm with the long axis of the femur. The therapist drives a rapid, powerful, axial posterior shearing force straight down through the femur, thrusting the ilium posteriorly against the stabilized sacrum.
• Diagnostic Power: The Thigh Thrust is one of the most sensitive single tests in the cluster (sensitivity reported around 88%).
• Positive Finding: Reproduction of focal familiar pain within the posterior sacroiliac joint.

4. Sacral Thrust Test (Prone Springing Test)

• Patient Position: Prone with the spine and lower extremities relaxed in neutral.
• Therapist Setup: The therapist stands beside the table, placing the hypothenar eminence or pisiform of the contact hand directly over the midline of the sacral apex or mid-sacrum (S2–S4 levels), pointing cranial-to-caudal. The second hand reinforces the contact hand.
• Execution: The therapist delivers a firm, rapid, anteriorly directed spring or thrust perpendicular to the plane of the sacrum, translating the sacrum anteriorly relative to the anchored iliac bones.
• Positive Finding: Reproduction of the patient's familiar sacroiliac pain.
• Target Tissue: Stresses the posterior interosseous ligaments and shearing mechanics of the sacroiliac syndesmosis.

5. Gaenslen's Test (Pelvic Torsion Test)

• Patient Position: Supine with the patient positioned close to the edge of the examination table.
• Execution: The patient actively flexes the non-tested hip and knee to the chest and grasps the knee firmly with both hands, locking the lumbar spine and contralateral hemipelvis into full posterior tilt. The leg on the tested side is allowed to drop off the lateral edge of the table into passive hyperextension. The therapist places one hand on the flexed knee and the other hand over the anterior distal thigh of the extended leg, applying simultaneous opposing overpressures (flexion on one side, extension on the other).
• Biomechanics: Induces vigorous opposing rotary torque (torsion) across the pelvic ring—posterior iliac rotation on the flexed side and anterior iliac rotation on the extended side.
• Positive Finding: Reproduction of familiar pain in the sacroiliac joint of either the flexed or extended extremity.

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4. Patrick's / FABER Test (Differential Diagnosis)

Patrick's test—commonly referred to by the acronym FABER (Flexion, ABduction, External Rotation) or the "Figure-Four Test"—is an indispensable diagnostic maneuver used to differentiate between coxofemoral (hip) joint disease and posterior sacroiliac pathology.

   PATIENT SUPINE: Figure-4 Position (Hip Flexed, Abducted, Externally Rotated)
   Therapist stabilizes contralateral ASIS + downward overpressure on medial knee
                                   |
               +-------------------+-------------------+
               |                                       |
       ANTERIOR GROIN PAIN                     POSTERIOR BUTTOCK PAIN
               |                                       |
       HIP JOINT PATHOLOGY                   SACROILIAC JOINT PATHOLOGY
   - Femoroacetabular Impingement (FAI)      - Sacroiliac Joint Dysfunction
   - Hip Osteoarthritis                      - Sacroiliitis
   - Acetabular Labral Tear                  - Sacroiliac Ligament Sprain

Procedure

1. The patient lies supine with legs extended.
2. The therapist passively flexes, abducts, and externally rotates the hip of the tested limb, resting the lateral malleolus of the tested foot across the anterior distal thigh/knee of the contralateral extended leg (creating a "figure-4").
3. The therapist stabilizes the patient's contralateral pelvis by placing one hand firmly over the contralateral ASIS to prevent pelvic rotation.
4. With the other hand, the therapist applies a gentle, progressive downward vertical overpressure against the medial aspect of the flexed knee, moving it toward the surface of the table.

Differential Interpretation

• Anterior Groin or Inguinal Pain: Indicates intra-articular hip joint pathology, including hip osteoarthritis, femoroacetabular impingement (FAI), capsular contracture, loose bodies, or an acetabular labral tear.
• Posterior Sacroiliac / Buttock Pain: Indicates sacroiliac joint pathology on the ipsilateral side, as the external rotation and abduction moment levers the femoral head into the acetabulum, transmitting posterior torque into the sacroiliac ligaments.
• Restricted Range Without Sharp Joint Pain: Inability of the knee to lower to within 4 cm of parallel to the table, accompanied by a soft or muscular end-feel, indicates hypertonicity or contracture of the iliopsoas, pectineus, or hip adductor musculature rather than true articular pathology.

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5. Biomechanical Mobility Assessment: Gillet's / Stork / Marching Test

While Laslett's cluster focuses strictly on pain provocation, Gillet's test (also known as the Stork test, Marching test, or kinetic test) assesses dynamic, functional iliosacral mobility during weight-bearing movement.

Biomechanical Principles

In a healthy pelvic girdle, when an individual stands unipedally on one foot and flexes the contralateral hip to 90° or greater, the ipsilateral ilium on the flexing side rotates posteriorly relative to the sacrum. This posterior rotation causes the posterior superior iliac spine (PSIS) on the flexing side to glide inferiorly and slightly laterally relative to the stationary S2 spinous process of the sacrum.

Procedure

1. The patient stands upright facing away from the therapist, with feet positioned hip-width apart. The patient may lightly rest their fingertips against a treatment table or wall for balance.
2. The therapist sits or kneels behind the patient, placing one thumb firmly on the inferior aspect of the ipsilateral PSIS and the other thumb horizontally aligned on the S2 spinous process of the sacrum.
3. The patient is instructed to stand firmly on the contralateral leg and actively flex the ipsilateral hip and knee to 90° or higher, bringing the knee toward the chest (mimicking a high marching step).
4. The therapist observes and palpates the relative spatial excursion of the two thumbs.

Clinical Findings

• Reliability Caution: Motion-palpation tests such as Gillet's have poor inter-rater reliability in research, so findings are combined with pain-provocation tests rather than used alone.
• Normal Mobility: The thumb on the PSIS moves distinctly inferiorly (approximately 0.5 to 1.5 cm) relative to the thumb on the S2 spinous process as the ilium rotates posteriorly during hip flexion.
• Hypomobility / Articular Fixation (Positive Stork Sign): The thumb on the PSIS fails to drop inferiorly; instead, it remains stationary, moves upward (superiorly), or the entire pelvis elevates as a rigid block. This indicates sacroiliac hypomobility, posterior rotation restriction, or mechanical articular fixation on the tested side.
• Contralateral Stance Phase Evaluation: By keeping one thumb on S2 and the other on the PSIS of the weight-bearing leg while the patient lifts the opposite leg, the therapist evaluates sacral movement relative to the ilium during weight-bearing (the sacrum should move inferiorly and anteriorly [nutation]; failure to move indicates a stance-phase sacroiliac fixation).

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6. Sacroiliac Joint & Pelvic Girdle Assessment Matrix

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7. Clinical Application Vignette

A 31-year-old female distance runner, who gave birth 6 months ago, presents with unilateral right deep buttock pain and localized tenderness over the right posterior superior iliac spine (Fortin's area). The pain worsens during single-leg stance, stair climbing, and transitioning from sitting to standing.

During assessment:

• Lumbar Spine Screening: Active lumbar flexion, extension, and repeated extension movements produce no radicular symptoms and do not alter or centralize the buttock ache (ruling out discogenic centralization).
• Laslett's Pain Provocation Cluster:
  • SI Distraction: Strongly reproduces deep right buttock pain.
  • Thigh Thrust: Immediately reproduces sharp, familiar right SIJ pain.
  • SI Compression: Reproduces the right buttock pain at 15 seconds of sustained pressure.
  • Gaenslen's and Sacral Thrust: Both reproduce localized posterior pelvic ache.
  • Result: All provocation tests positive (well beyond the threshold of 2 or more of the 4 key tests).
• Patrick's (FABER) Test: Downward pressure on the right flexed knee produces familiar posterior buttock pain over the right SIJ, with no groin pain reported (ruling out hip osteoarthritis or labral tear).
• Gillet's (Stork) Test: When flexing the right hip, the right PSIS moves superiorly and laterally rather than dropping inferiorly relative to S2, confirming right sacroiliac joint hypomobility and articular dysfunction.

Clinical Reasoning: The strongly positive provocation cluster, combined with posterior pain on the FABER test and no centralization, makes the right sacroiliac joint the most likely pain source. Gillet's test suggests reduced posterior iliac rotation, although motion-palpation tests such as Gillet's have poor inter-rater reliability and are interpreted cautiously. The therapist formulates a comprehensive treatment plan incorporating myofascial release to the hypertonic piriformis, gluteus medius, and quadratus lumborum, gentle grade II–III sacroiliac joint mobilizations to restore posterior rotation, and remedial strengthening of the posterior oblique force closure sling (gluteus maximus and contralateral latissimus dorsi).