Comprehensive Diagnostic Approach for the Sacroiliac (SI) Joint

Sacroiliac (SI) joint problems require appropriate interpretation of a patient’s history, clinical exam results, and imaging studies. Differential diagnostic approach, including the SI joint, the spine, and the hip, must be used to accurately assess and identify the actual pain generator(s).

Lower Back Pain SI Joint Pelvis Image

During physical exam, patients with sacroiliac (SI) joint pain may exhibit any/all of the following symptoms:

  • Low back pain
  • Palpable tenderness of the posterior pelvic sacroiliac (SI) region
  • Pain from provocative maneuvers to the hip (i.e. Faber test) and the absence of neurologic deficit
  • Joint asymmetry as seen on CT and MRI.

When the SI joint is suspected as the source of the patient’s low back pain, confirmation is provided by CT or fluoroscopic guided injection. This injection is the diagnostic "litmus test." If lidocaine is injected into the joint and symptoms temporarily resolve, this is confirmation of the SI joint as the source, or a source, of the patient’s low back pain (as multiple pain generators may co-exist).

Evaluating the SI Joint

A comprehensive approach to SI joint evaluation might look like this:

  • Recognize patient history of SI joint problems
  • Perform physical examination:
    • Palpation
    • Provocative tests (minimum 3 out of 5 tests should be positive)
  • Review or order imaging studies – for abnormalities / asymmetry
  • Administer diagnostic injections (75% pain relief from one injection, or 50% pain relief from two injections to confirm SI joint diagnosis)
Management Algorithm for SI Joint Complaints

View Video:
Basics of the SI Joint Exam

Provocative Tests for Sacroiliac (SI) Joint Disorders

After assessing the patient for existence of tenderness upon palpation, there are a series of provocation tests that will generate pain in patients with SI joint problems and should be included in the examination. The rule of thumb for a positive diagnosis of the SI joint as a pain generator is pain provoked in at least 3 out of 5 of the following tests:

View Video:
Diagnosing SI Joint Disorders: Provocative Testing

Provocative tests:

FABER - (Flexion, ABduction, External Rotation)

Applies tensile force on the anterior aspect of the SI joints

The patient lies supine as the examiner crosses the same-side foot over the opposite-side thigh. The pelvis is stabilized at the opposite ASIS with the hand of the examiner.

A gentle force is steadily increased on the same side knee of the patient, exaggerating the motion of hip flexion, abduction, and external rotation.



Applies lateral compression force across the SI joints

The patient is placed in a side-lying position, facing away from the examiner, with a pillow between the knees.

The examiner places a steady downward pressure through the anterior aspect of the lateral ilium, between the greater trochanter and iliac crest.


Thigh Thrust

Applies anteroposterior shear stress on the SI joint

The patient lies supine with one hip flexed to 90 degrees. The pelvis is stabilized at the opposite ASIS with the hand of the examiner.

The examiner stands on the same side as the flexed leg. The examiner provides steady increasing pressure through the axis of the femur.

thigh thrust


Applies tensile forces on the anterior aspect of the SI joints

The patient lies supine and is asked to place their forearm behind their lumbar spine to support the natural lordosis.

A pillow is placed under the patient’s knees. The examiner places their hands on the anterior and medial aspects of the patient’s left and right ASIS with arms crossed and elbows straight.

A slow and steady pressure is applied by leaning toward the patient.

Thigh Thrust


Applies torsional stress on the SI joints 

The patient lies supine near the edge of the table and is asked to flex the opposite hip grasping their knee. This action "locks" the SI joint in position prior to the next step.

The examiner then slides the near-side leg (typically starting with the painful side) off the table and applies a steady extension force while simultaneously applying a flexion force through the opposite leg. The patient assists with the opposite-side hip flexion.



Diagnostic SIJ injection

If, following the injection, the patient's pain is decreased a significant amount, then it can be concluded that the SI joint is either the source, or a major contributor, to the low back pain.1

  • Posterior & inferior approach
  • 22 gauge 5" styletted needle
  • 0.25ml contrast medium
  • 1.25ml Lidocaine


1. Dreyfuss, Paul et al. "Sacroiliac Joint Pain." J Am Acad Orthop Surg 2004;12:255-265.

Sacroiliac (SI) Joint Injection Technique

The most common means for confirming sacroiliac joint disorders is an injection with CT or fluoroscopic guidance to confirm accurate placement of the needle into the SI joint. The pain response indicates the role of the SI joint in each case:

  • If no pain improvement, then test was negative. SI joint is not a pain generator.
  • If > 75% pain improvement, then test was positive. SI joint is considered a pain generator.
  • If 50-75% pain improvement, then test was equivocal. Repeat to confirm SI joint as a pain generator, and consider the existence of multiple pain generators.

If symptoms are decreased by a minimum of 75% with one injection or by 50% each time with two injections, it can be concluded that the SI joint is either the source, or a major contributor, to the particular patient's low back pain.

View Video:
Diagnosing SI Joint Disorders: Diagnostic Injection Demonstration

Reference Tools--Print out the following resources to aid in your diagnosis of Sacroiliac (SI) Joint Disorders:

If your patients have low back symptoms that are SI joint in origin, learn more about SI joint disorders and using a minimally invasive surgical (MIS) approach called the iFuse Implant System®.

The iFuse Implant System® is intended for sacroiliac joint fusion for conditions including sacroiliac joint dysfunction that is a direct result of sacroiliac joint disruptions and degenerative sacroiliitis. The iFuse Implant System® is intended for sacroiliac fusion for conditions including sacroiliac joint dysfunction that is a direct result of sacroiliac joint disruption and degenerative sacroiliitis. This includes conditions whose symptoms began during pregnancy or in the peripartum period and have persisted postpartum for more than 6 months. Clinical studies have demonstrated that treatment with the iFuse Implant System improved pain, patient function, and quality of life at 12 months post-implantation. There are potential risks associated with the iFuse Implant System. It may not be appropriate for all patients and all patients may not benefit. For information about the risks, click here.

More Resources in the Physicians Center