Sacroiliac Joint (SIJ) Dysfunction: Diagnosis, Tests, and Differential Diagnosis

How is SIJ diagnosed?

Diagnosing Sacroiliac Joint (SIJ) dysfunction is a complex process that relies on a combination of detailed patient history, a thorough physical examination with specific provocation tests, imaging studies to rule out other conditions, and most definitively, diagnostic injections.

Understanding Sacroiliac Joint (SIJ) Dysfunction

The sacroiliac joints are two small, sturdy joints connecting the sacrum (the triangular bone at the base of the spine) to the ilium (the large bones of the pelvis). While they have limited movement, they play a crucial role in absorbing shock, transferring weight between the upper body and legs, and providing stability to the pelvis. When these joints become inflamed or dysfunctional, they can cause significant pain, often referred to as SIJ dysfunction or sacroiliitis (inflammation of the SIJ).

Symptoms commonly include:

• Unilateral lower back pain, often below the L5 vertebra.
• Pain in the buttock, hip, or groin.
• Pain that radiates down the leg, mimicking sciatica.
• Increased pain with prolonged sitting or standing, stair climbing, or walking.
• Pain when transitioning from sitting to standing.
• Pain with single-leg stance or activities that load one leg.

The Challenge of SIJ Diagnosis

Diagnosing SIJ dysfunction can be challenging due to several factors:

• Mimicry of Symptoms: SIJ pain often presents similarly to other common conditions, such as lumbar disc herniations, facet joint arthritis, hip pathology, and piriformis syndrome.
• No Single Definitive Test: Unlike some conditions that can be confirmed with a single blood test or imaging scan, SIJ dysfunction is diagnosed through a cluster of findings.
• Variability in Presentation: Symptoms can vary widely between individuals, making a standardized approach difficult.

The Comprehensive Diagnostic Process

A skilled clinician will employ a multi-faceted approach to accurately diagnose SIJ dysfunction, systematically ruling out other potential pain generators.

Patient History and Symptom Presentation

The diagnostic process begins with a detailed medical history, focusing on the onset, nature, location, and aggravating/alleviating factors of the pain. Key questions include:

• Mechanism of Injury: Was there a specific trauma, fall onto the buttocks, motor vehicle accident, or repetitive stress?
• Pain Location: Is the pain primarily in one buttock, directly over the SIJ, or does it radiate?
• Aggravating Factors: Does pain worsen with sitting, standing, walking, bending, twisting, or weight-bearing on one leg (e.g., climbing stairs)?
• Alleviating Factors: What makes the pain better?
• Associated Symptoms: Are there any neurological symptoms like numbness, tingling, or weakness?
• Past Medical History: History of inflammatory arthritis, pregnancy, or prior spinal surgery can be relevant.

Physical Examination

A thorough physical examination is crucial, involving observation, palpation, and specific provocative tests designed to stress the SIJ and reproduce pain.

• Palpation: Tenderness directly over the SIJ (just medial and inferior to the posterior superior iliac spine, PSIS) is often noted.
• Provocation Tests: These tests load the SIJ in different directions. A "cluster" of at least three positive tests significantly increases the probability of SIJ pain. Common tests include:
  • Thigh Thrust Test (Posterior Shear Test): Applies posterior shear force to the SIJ.
  • Distraction Test (Gapping Test): Applies anterior distraction force to the SIJ.
  • Compression Test (Sacral Compression Test): Applies medial compression force to the SIJ.
  • FABER Test (Flexion, Abduction, External Rotation/Patrick's Test): Stresses both the hip and SIJ.
  • Gaenslen's Test: Stresses one SIJ while the other hip is flexed.
  • Yeoman's Test: Extends the hip with knee flexion, stressing the SIJ.

Imaging Studies

Imaging is primarily used to rule out other conditions or identify underlying structural pathologies, rather than directly diagnosing SIJ pain as the source.

• X-rays: Can show degenerative changes, fractures, or signs of inflammatory arthritis (sacroiliitis). However, normal X-rays do not rule out SIJ dysfunction, and degenerative changes may be asymptomatic.
• Magnetic Resonance Imaging (MRI): Provides detailed images of soft tissues and can detect inflammation (edema) within or around the joint, stress fractures, or signs of inflammatory sacroiliitis. It is particularly useful for ruling out disc pathology or other spinal issues.
• Computed Tomography (CT) Scans: Offers more detailed bone imaging and can be useful for assessing complex bony anatomy or subtle fractures.

It's important to note that many individuals with SIJ pain will have normal imaging findings, or imaging may show degenerative changes that are not the primary source of their pain.

Diagnostic Injections: The Gold Standard

For confirmation, a diagnostic SIJ injection is often considered the most definitive test.

• Procedure: Under fluoroscopic (X-ray) or ultrasound guidance, a local anesthetic (and often a corticosteroid) is injected directly into the SIJ. The imaging guidance ensures accurate placement of the needle.
• Interpretation: If the injection results in significant (e.g., 50-75% or greater) and temporary reduction of pain, it strongly indicates that the SIJ is the primary pain generator. Sometimes, a second injection with a different anesthetic is performed to confirm the diagnosis.

Differential Diagnosis: Ruling Out Other Conditions

A crucial part of the diagnostic process is systematically ruling out other conditions that can cause similar pain. These include:

• Lumbar Spine Pathology: Disc herniation, spinal stenosis, facet joint arthritis, or spondylolisthesis.
• Hip Pathology: Osteoarthritis of the hip, labral tears, femoroacetabular impingement (FAI), or trochanteric bursitis.
• Piriformis Syndrome: Compression of the sciatic nerve by the piriformis muscle.
• Referred Pain: From visceral organs, though less common for isolated lower back/buttock pain.
• Inflammatory Arthritis: Conditions like ankylosing spondylitis, psoriatic arthritis, or reactive arthritis can cause sacroiliitis.

Conclusion

Diagnosing sacroiliac joint dysfunction requires a skilled clinician who can synthesize information from a detailed patient history, a comprehensive physical examination with specific provocation tests, and judicious use of imaging. While imaging can rule out other conditions, the diagnostic SIJ injection remains the most reliable method for confirming the SIJ as the source of pain. An accurate diagnosis is paramount, as it guides the development of an effective, targeted treatment plan, whether conservative or interventional.