Sacroiliac (SI) Joint Pain: A Practical Clinical Guide to Diagnosis

Author: Dr Tasrif Hamdi

Sacroiliac (SI) joint pain is a common and frequently missed cause of low back pain. Because the symptoms can mimic those of lumbar disc problems, facet pain, hip disorders, or myofascial pain, a structured approach—comprising a thorough history, focused examination, and confirmatory diagnostic blocks—helps identify the SI joint as the source of the pain.

What is the SI joint, and why can it cause pain?

The sacroiliac joints sit between the sacrum and ilium and function primarily as load-transfer joints. They are designed more for stability than movement. When stability is compromised—due to ligament strain, altered pelvic mechanics, or muscle imbalance—the SI joint complex can become inflamed and painful.

Key anatomy (clinically relevant)

  • The SI joint is among the largest true axial synovial joints.
  • The joint surfaces and surrounding ligaments are built to bear load and resist shear.
  • Ligamentous support is a major contributor to SI joint stability; weakness or overload can accelerate irritation and degeneration.

How common is SI joint pain?

SI joint pain is an important contributor to axial low back pain. In clinical practice, a meaningful proportion of patients presenting with low back pain may have the SI joint as the main source of pain, which is why SI joint screening tests are valuable in routine back pain evaluation.

Common causes of SI joint pain

Traumatic causes

  • Fall onto the buttocks
  • Pelvic trauma
  • Motor vehicle accidents
  • Sudden lifting, twisting, or repetitive strain

Non-traumatic/biomechanical causes

  • Pregnancy-related pelvic changes
  • Leg length discrepancy
  • Abnormal gait or pelvic asymmetry
  • Scoliosis or chronic postural imbalance
  • Post-lumbar fusion altered biomechanics

Inflammatory and other medical causes

  • Spondyloarthropathy
  • Osteoarthritis
  • Enthesopathy
  • Infection (rare but important to consider)

Typical pain location and referral pattern

SI joint pain is most commonly felt:

  • Over the buttock region near the posterior pelvis

It may also refer to:

  • Lower lumbar area
  • Groin
  • Abdomen (occasionally)
  • Down the thigh, and in some cases even toward the foot

Because referral patterns overlap with lumbar radiculopathy and hip pathology, physical examination is critical.

Symptoms: what makes SI joint pain worse or better?

Common aggravating activities

  • Sitting for long periods
  • Sit-to-stand transitions
  • Prolonged walking
  • Climbing stairs
  • Rolling onto the painful side in bed

Common relieving factors

  • Lying on the non-painful side
  • Shifting weight to the non-painful side

Physical examination: the most useful SI joint provocation tests

No single test is perfect. In practice, a cluster of positive provocation tests increases the likelihood that the SI joint is involved.

1) Compression (Approximation) Test

  • Patient lies on the side with hips and knees flexed.
  • Downward force is applied through the upper iliac crest to compress the SI joints.
  • Reproduction of familiar pain suggests SI joint involvement.

2) Distraction (Gapping) Test

  • Patient lies supine.
  • Posteriorly directed pressure is applied to both ASIS to stress the anterior SI structures.
  • Familiar pain reproduction supports SI joint pathology.

3) FABER (Patrick’s) Test

  • Patient lies supine; the affected foot is placed on the opposite knee.
  • The hip is gently pressed into abduction and external rotation while stabilizing the opposite pelvis.
  • Buttock-dominant pain increases suspicion of SI joint involvement (groin pain may point more to hip pathology).

4) Gaenslen’s Test

  • Patient lies supine near the edge of the table.
  • One hip is maximally flexed while the other leg is allowed to extend off the table.
  • Pain reproduced in the SI region suggests SI dysfunction on the side of the extended leg.

5) Thigh Thrust (Posterior Shear) Test

  • Patient lies supine.
  • The affected hip is flexed to ~90° with slight adduction.
  • Force is applied through the femur to shear the SI joint.
  • Reproduction of familiar pain supports SI joint involvement.

6) Fortin Finger Test

  • The patient points with one finger to the pain location consistently.
  • Typical SI pain is localized inferomedial to the PSIS.
  • A consistent, focal point increases the likelihood of SI origin.

7) Gillet Test (Motion Test)

  • Examiner palpates the PSIS on the tested side and the sacrum (around S2).
  • The patient lifts the tested leg (hip flexion).
  • Abnormal/limited PSIS movement compared to expected motion suggests SI dysfunction (interpret in combination with provocation tests).

Imaging for SI joint pain: what it can and cannot do

Imaging may help rule out other pathology or identify inflammatory patterns, but:

  • Abnormal imaging does not prove the SI joint is the pain source.
  • Normal imaging does not exclude SI joint pain.

For many patients, diagnosis remains primarily clinical and is strengthened by confirmatory blocks when indicated.

Confirming SI joint pain: Diagnostic SI joint block

When history and provocation tests strongly suggest SI joint pain—or when diagnosis remains uncertain—a diagnostic intra-articular SI joint injection (local anesthetic block) can be used to confirm the SI joint as the pain generator.

Practical interpretation

  • Significant, consistent pain relief immediately after local anesthetic suggests the SI joint is the primary pain source.
  • Relief must be interpreted carefully because false positives/negatives can occur.

Why diagnostic blocks can be misleading

  • Local anesthetic spread to nearby structures (ligaments, muscles, nerve roots)
  • Excessive superficial anesthesia or sedation masking pain reporting
  • Inadequate intra-articular delivery leading to false negatives

A practical diagnostic approach (clinic-friendly)

  1. Suspect SI joint pain based on buttock-dominant pain pattern and aggravating activities.
  2. Perform multiple SI provocation tests.
  3. If several tests reproduce the patient’s typical pain, SI joint involvement is likely.
  4. Use imaging selectively to evaluate differentials or inflammatory disease.
  5. If needed, confirm with a diagnostic SI joint block before committing to targeted interventional treatment plans.

When to seek specialist evaluation urgently

Seek prompt evaluation if low back/pelvic pain is associated with:

  • Fever, systemic illness, or suspected infection
  • Recent significant trauma
  • Progressive neurological deficits
  • Unexplained weight loss or malignancy red flags
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FAQs (SEO)

What is the most common location of SI joint pain?

Most patients feel SI joint pain in the buttock region near the back of the pelvis, often close to the PSIS area.

Which tests are most useful for diagnosing SI joint pain?

A cluster of positive provocation tests—such as thigh thrust, FABER, Gaenslen, compression, and distraction—improves diagnostic confidence.

Can MRI confirm SI joint pain?

MRI can help evaluate inflammatory disease or rule out other conditions, but imaging alone cannot confirm that the SI joint is the pain generator.

What confirms SI joint pain most reliably?

A diagnostic intra-articular SI joint local anesthetic block producing significant, consistent pain relief is commonly used to confirm SI joint origin.

Reviewed by: Dr Gautam Das

About the Author

Dr. Tasrif Hamdi, MD, PhD is a pain management specialist and academic anesthesiologist based in Medan, Indonesia. He serves as Head of the Department of Anesthesiology and Intensive Therapy at the Faculty of Medicine, Universitas Sumatra Utara, and practices at Haji Adam Malik Hospital, one of the major tertiary care centers in North Sumatra.

He completed his medical degree, anesthesiology specialization, advanced pain management consultant training, and PhD in medical sciences in Indonesia, with formal training in anesthesiology, intensive care, and interventional pain management.

Dr. Hamdi has been actively involved in teaching pain management and minimally invasive anesthesia to postgraduate trainees and is a frequent speaker at national scientific meetings in Indonesia. His academic work includes multiple peer-reviewed publications and textbooks related to pain mechanisms, cancer pain, regional anesthesia, and interventional pain procedures.

His clinical and research interests include:

  • Chronic low back pain
  • Sacroiliac joint pain
  • Interventional pain procedures
  • Cancer pain management
  • Multimodal analgesia strategies

Through clinical practice, research, and medical education, he contributes to the advancement of pain medicine in Indonesia and the wider Southeast Asian region.