Sacroiliac (SI) Joint Pain: Understanding, Symptoms, and Diagnostic Tests

What are the three tests to tell you if your back pain is caused by SI?

Identifying sacroiliac (SI) joint dysfunction as a cause of lower back pain often involves a series of provocative tests designed to reproduce pain by stressing the joint, with three common and effective tests being the Faber Test, Thigh Thrust Test, and SI Joint Compression Test.

Understanding Sacroiliac (SI) Joint Pain

The sacroiliac (SI) joints are two large, L-shaped joints connecting your sacrum (the triangular bone at the base of your spine) to your iliac bones (the large bones of your pelvis). While they have limited movement, their primary role is to provide stability and absorb shock, transferring load between your upper body and lower extremities. Dysfunction in one or both SI joints can lead to significant pain, often mimicking other conditions such as lumbar disc herniations, sciatica, or hip problems, making accurate diagnosis challenging.

Pain originating from the SI joint is commonly referred to as sacroiliac joint dysfunction, sacroiliitis (inflammation of the joint), or SI joint syndrome. It can result from various factors, including trauma, repetitive stress, leg length discrepancies, gait abnormalities, pregnancy, or degenerative changes.

The Challenge of Diagnosing SI Joint Pain

Due to the SI joint's proximity to the lumbar spine and hip, pain referral patterns can be complex and misleading. Patients often report pain in the lower back, buttock, groin, or even radiating down the leg. This overlap necessitates a thorough examination, including specific physical provocation tests, to help isolate the SI joint as the primary pain generator. While no single test is 100% accurate, a cluster of positive findings from multiple tests significantly increases the likelihood of SI joint involvement.

Key Indicators of SI Joint Involvement

Before performing specific tests, consider common symptoms that may point towards SI joint dysfunction:

• Localized Pain: Deep, aching pain in the lower back or buttock, often on one side.
• Radiating Pain: Pain that can refer to the groin, hip, or down the back of the thigh, sometimes mimicking sciatica.
• Pain with Transitional Movements: Increased pain when moving from sitting to standing, turning in bed, or climbing stairs.
• Pain with Single-Leg Loading: Discomfort when standing on one leg, walking, or running.
• Stiffness: Morning stiffness in the lower back or pelvis.
• Tenderness: Palpable tenderness over the SI joint itself.

Three Provocation Tests for SI Joint Pain

These tests are designed to apply stress to the SI joint, and a reproduction of your typical pain indicates a positive result. Always perform these tests gently and stop if severe pain occurs. It is advisable to have a trained professional conduct or supervise these assessments.

1. The Faber Test (Flexion, Abduction, External Rotation Test)

• Purpose: To stress the anterior (front) aspect of the SI joint and assess for pain originating from the joint or hip pathology.
• Procedure:
  • The individual lies on their back (supine) on a firm surface.
  • The examiner passively flexes the individual's hip, abducts it (moves it away from the midline), and externally rotates it so that the ankle of the tested leg rests on the opposite knee. This forms a "figure-4" position.
  • The examiner then places one hand on the anterior superior iliac spine (ASIS) of the opposite, non-tested side to stabilize the pelvis.
  • With the other hand, the examiner gently but firmly applies a downward pressure to the medial aspect of the flexed knee, attempting to push the knee towards the surface.
• Positive Sign: The reproduction of pain in the SI joint region (buttock or lower back) on the side being tested. Hip pain would indicate a different pathology.

2. The Thigh Thrust Test (Posterior Pelvic Pain Provocation Test)

• Purpose: To stress the posterior (back) aspect of the SI joint by applying a shearing force.
• Procedure:
  • The individual lies on their back (supine).
  • The examiner flexes the individual's hip to 90 degrees and also flexes the knee of the tested leg.
  • The examiner places one hand under the sacrum to stabilize the pelvis.
  • With the other hand, the examiner applies a strong, posterior (downward and slightly in) force through the femur (thigh bone) along the line of the femur's shaft. This force is directed towards the SI joint.
• Positive Sign: The reproduction of pain in the SI joint region (buttock or lower back) on the side being tested.

3. SI Joint Compression Test

• Purpose: To compress the SI joints, provoking pain if the joint is inflamed or dysfunctional.
• Procedure:
  • The individual lies on their back (supine).
  • The examiner places both hands over the anterior superior iliac spines (ASIS) of the individual's pelvis.
  • The examiner then applies a strong, steady downward and outward pressure through the ASIS, effectively compressing the SI joints together.
• Positive Sign: The reproduction of pain in the SI joint region.

Interpreting the Test Results

It's crucial to understand that a single positive test does not definitively diagnose SI joint pain. The most reliable indicator is a "cluster" of positive findings – meaning pain is reproduced in at least three out of five common SI joint provocation tests (the three listed above, plus Gaenslen's Test and the Distraction Test). If multiple tests consistently reproduce your typical SI joint pain, it strongly suggests that the SI joint is a primary source of your discomfort.

Important Considerations and Professional Diagnosis

While these tests are valuable tools for screening and indication, they are not a substitute for a comprehensive medical evaluation. If you suspect your back pain is related to your SI joint, or if you experience persistent or worsening pain, you should:

• Consult a Healthcare Professional: Seek evaluation from a qualified physician, physical therapist, or chiropractor. They can perform a thorough physical examination, consider your full medical history, and rule out other potential causes of your pain.
• Diagnostic Injections: In some cases, a diagnostic injection of anesthetic into the SI joint may be performed. If the injection provides significant temporary pain relief, it further supports the diagnosis of SI joint dysfunction.
• Imaging: While X-rays, MRI, or CT scans typically do not show SI joint dysfunction clearly unless there is significant degeneration or inflammation, they may be used to rule out other spinal or hip pathologies.

Beyond Diagnosis: Management and Next Steps

Once SI joint dysfunction is suspected or diagnosed, a comprehensive management plan can be developed. This often includes:

• Manual Therapy: Techniques to restore proper joint mechanics.
• Targeted Exercises: Strengthening core muscles, glutes, and muscles that stabilize the pelvis.
• Stretching: Addressing muscle imbalances and tightness.
• Activity Modification: Identifying and avoiding movements or positions that aggravate the pain.
• Pain Management: Modalities like heat/cold therapy, anti-inflammatory medications, or in some cases, corticosteroid injections.

Understanding the role of the SI joint and utilizing these specific provocation tests can be a crucial step in identifying the true source of your lower back pain, guiding you toward effective treatment and recovery.