How Doctors Confirm That Pain Is Coming From the SI Joint

Sacroiliac joint pain is one of the more challenging diagnoses in spine and orthopedic medicine — not because the condition is rare, but because its symptoms overlap substantially with lumbar disc disease, hip arthritis, and other pain generators. Confirming that the SI joint is the actual source of pain requires a systematic approach that combines multiple types of information.

The American Academy of Orthopaedic Surgeons identifies an image-guided local anesthetic injection into the SI joint as the "gold standard for diagnosing SI joint pain."

This reflects the fundamental challenge: no single examination finding, imaging result, or symptom pattern is specific enough on its own to confirm the diagnosis. The diagnostic injection — which tests whether numbing the joint substantially reduces the patient's usual pain — provides the most direct evidence that the SI joint is the primary pain source.

Medical source: American Academy of Orthopaedic Surgeons, OrthoInfo — Sacroiliac Joint Dysfunction. orthoinfo.aaos.org

A detailed pain history is the starting point. Key questions include:

• Where exactly is the pain, and does it radiate? (See: Where Is SI Joint Pain Usually Felt?)
• What makes it better or worse? (Sitting, standing, walking, climbing stairs, rolling over in bed)
• Was there a precipitating event? (Pregnancy, fall, prior lumbar surgery, trauma)
• How long have symptoms been present, and how have they changed?

Certain historical features raise the probability of SI joint involvement — particularly pain that is worse with prolonged sitting or standing on one leg, and pain that is reproduced by specific activities involving the pelvis.

The physical examination includes assessment of the lumbar spine, hips, and SI joints. Several provocative maneuvers have been studied for their ability to reproduce SI joint pain:

• FABER test (Flexion, ABduction, External Rotation) — stresses the SI joint and hip
• FADIR test (Flexion, ADduction, Internal Rotation) — primarily stresses the hip but can implicate the SI joint
• Distraction and compression tests — apply force across the SI joint
• Thigh thrust test — applies posterior shear force to the SI joint
• Gaenslen's test — stresses the SI joint through hip hyperextension

No single test is definitive. Studies suggest that a cluster of three or more positive provocative tests increases the probability of SI joint pain, but the sensitivity and specificity of individual tests are modest.

Imaging of the SI joint — including X-ray, CT, and MRI — can identify structural changes such as sacroiliitis, fractures, or inflammatory arthropathy. However, imaging findings do not reliably predict whether the SI joint is the source of a patient's pain. Degenerative changes are common in asymptomatic individuals, and a normal-appearing SI joint on imaging does not exclude it as a pain source.

Imaging is most useful for excluding other diagnoses (lumbar disc herniation, hip arthritis, fracture) and for identifying inflammatory conditions such as ankylosing spondylitis.

When the history, examination, and imaging are consistent with SI joint pain but the diagnosis remains uncertain, an image-guided diagnostic injection is the most reliable next step. Under fluoroscopic or CT guidance, a small volume of local anesthetic is injected into the SI joint. If the patient experiences substantial relief of their usual pain — typically defined as 75% or greater reduction — this confirms the SI joint as the primary pain generator and guides subsequent treatment decisions.

The diagnostic injection is discussed in more detail in the related article below.

Dr. Blythe uses a structured diagnostic approach that integrates all four components above. Treatment is not recommended based on symptom location alone. When a diagnostic injection is indicated, it is performed under image guidance to ensure accurate needle placement and reliable results.

Related articles: Where Is SI Joint Pain Usually Felt? · Diagnostic vs. Therapeutic SI Joint Injections · SI Joint Pain or Something Else?

Ready to discuss your symptoms? Request an appointment or call 405-418-4500.

Medical review date: July 2026