What is the recommended workup and treatment for a patient with sacroiliac (SI) joint pain?

SI Joint Workup

Begin with plain radiographs of the SI joints and spine as the initial imaging study for suspected inflammatory sacroiliitis or spondyloarthropathy. 1

Initial Clinical Assessment

History and Physical Examination

• Look for inflammatory symptoms: Pain duration >3 months, age <45 years, morning stiffness, improvement with exercise, and alternating buttock pain 1
• Perform provocative maneuvers: At least 3 positive tests are required to achieve 94% sensitivity and 78% specificity for SI joint pain (validated against dual fluoroscopically-guided anesthetic injections with ≥80% pain reduction) 2
• Key provocative tests include: Thigh thrust, FABER's test, lateral compression, Gaenslen's test, and distraction test 2, 3
• Note the specificity drop: With only 2 positive tests specificity falls to 66%, and with 1 positive test it drops to 44%, dramatically increasing misdiagnosis risk 2

Imaging Algorithm

Step 1: Initial Imaging (Suspected Inflammatory Sacroiliitis)

• X-ray SI joints (Rating 9/9 - "usually appropriate") 1
• X-ray spine as complementary examination (Rating 9/9) 1
• Do NOT order: MRI, CT, bone scan, PET/CT, or ultrasound as initial studies (all rated 1/9 - "usually not appropriate") 1

Step 2: If Radiographs Negative or Equivocal

• MRI SI joints without IV contrast (Rating 8/9) as the preferred next step 1
• MRI SI joints with and without IV contrast (Rating 8/9) may be helpful for initial evaluation of inflammatory changes, though contrast does not significantly increase diagnostic accuracy 1
• CT SI joints without IV contrast (Rating 7/9) is an alternative for patients unable to undergo MRI, particularly useful for identifying subtle erosions 1
• MRI technical requirements: Must include fat-suppressed fluid-sensitive sequences (T2-weighted fat-suppressed or STIR images) 1

Step 3: If SI Joint Imaging Remains Negative

• MRI spine without IV contrast (Rating 8/9) to evaluate for isolated spine inflammatory involvement, which occurs in 6-23% of cases 1
• Notify the radiologist: Indicate the examination is for possible axial spondyloarthropathy as imaging sequences may need modification 1
• Sagittal imaging is the best plane for evaluation of axial spondyloarthropathy spinal lesions 1

Diagnostic Injection Protocol

Indications for Diagnostic Blocks

• Required before surgical intervention: Dual comparative blocks with anesthetic only (no corticosteroid) achieving >70-80% concordant pain relief 2, 4
• Diagnostic threshold: At least 70-80% pain relief confirms the SI joint as the primary pain generator with 78% specificity 2
• Duration requirement: Relief must last at least the duration of the local anesthetic to be considered valid 2

Critical Pitfall

• Single block is insufficient: Proceeding with only one diagnostic block reduces diagnostic accuracy and surgical success rates 4
• False positives exist: The validity of diagnostic blocks remains controversial due to potential for false-positive and false-negative results 3, 5

Treatment Algorithm

Conservative Management (First-Line)

• Physical therapy: Focused pelvic stabilization exercises specifically targeting the SI joint 2, 4
• Pharmacological treatment: NSAIDs and analgesics for symptom relief 3, 6
• Manual medicine and exercise therapy 3
• Cognitive-behavioral therapy if indicated 3

Interventional Options (After Conservative Failure)

1. Therapeutic SI joint injections with corticosteroid: Can produce pain relief for >3 months in some patients 2, 3

   • Consider peri-articular vs intra-articular: Peri-articular injections show response rates up to 100% vs 36% for intra-articular when extra-articular pain contributions exist 4

2. Prolotherapy with dextrose water: Superior results (64% achieving 50% pain relief at 6 months) compared to corticosteroid injections (27%) 2, 4

3. Radiofrequency ablation: Target L5 dorsal ramus and S1-3 (or S4) lateral branches 3

   • Cooled RFA demonstrates the strongest evidence with extensive lesioning strategies 3
   • Both continuous and pulsatile RFA are associated with good outcomes 7

Surgical Fusion Criteria

Only consider SI joint fusion if ALL of the following are met:

• ≥3 positive provocative maneuvers 2
• Dual diagnostic blocks with >70-80% concordant pain relief 2, 4
• Radiographic evidence of SI joint degeneration 8
• Failure of comprehensive conservative management including physical therapy, injections, and radiofrequency ablation 2, 4
• Preferred approach: Lateral transfixing technique (not posterior non-transfixing) 4

Follow-Up Imaging

For Known Axial Spondyloarthropathy

• Conventional radiography of SI joints and symptomatic spine regions is the primary method for following structural disease progression 1
• Frequency: No more frequently than every 2 years, based on individual symptoms 1
• MRI may be helpful for evaluation of treatment response 1

Special Consideration: Ankylosed Spine

High-Risk Fracture Scenario

• High clinical suspicion required: Patients with spine ankylosis have high incidence of unstable fractures from minor trauma 1
• Imaging required: Multiplanar CT is necessary to exclude fracture in ankylosed patients with spine pain after any trauma 1
• Add MRI without contrast if neurologic symptoms present to evaluate spinal cord, nerve root, and ligamentous injuries 1