What is the cause of right-sided sacroiliac pain that worsens with movement and bending and improves with heat and ibuprofen (Advil) in a 90-year-old female?

Right-Sided Sacroiliac Pain in a 90-Year-Old Female

The most likely cause is mechanical sacroiliac joint dysfunction or degenerative sacroiliitis, given the age, unilateral presentation, mechanical pain pattern (worse with movement/bending), and response to NSAIDs and heat—not inflammatory spondyloarthropathy.

Clinical Reasoning

Why This is Likely Mechanical/Degenerative Disease

The clinical presentation strongly suggests a non-inflammatory etiology for several key reasons:

• Age: At 90 years old, inflammatory axial spondyloarthropathy (axSpA) is highly unlikely as this typically presents in younger adults (20s-40s) 1
• Unilateral pain: Inflammatory sacroiliitis characteristically presents bilaterally, whereas mechanical SI joint pain is often unilateral 2, 3
• Mechanical pattern: Pain worsening with movement and bending suggests mechanical stress rather than inflammatory rest pain 2, 3
• Response to treatment: Improvement with heat and NSAIDs is consistent with degenerative joint disease; inflammatory back pain typically improves with exercise and worsens with rest 1

Differential Considerations

Sacroiliac joint dysfunction accounts for 16-30% of chronic mechanical low back pain cases and presents with gluteal region pain that may refer to the lower lumbar region 2, 4. The SI joint transfers large bending moments and compression loads, making it vulnerable to degenerative changes, particularly in elderly patients 4.

Osteoarthritis of the SI joint is common in this age group and produces similar symptoms—pain with weight-bearing, movement, and mechanical stress 5.

Less likely causes in this patient:

• Inflammatory spondyloarthropathy: Wrong age demographic and bilateral presentation expected 1
• Sacroiliac sprain: Typically follows acute injury 3
• Osteitis condensans ilii: Occurs in postpartum women 5

Diagnostic Approach

Initial Imaging

Plain radiographs of the pelvis/sacroiliac joints should be obtained first to evaluate for:

• Degenerative changes, sclerosis, and joint space narrowing 1
• Exclusion of fractures or other "red flag" pathology 2
• Assessment of structural abnormalities 1

The American College of Radiology rates X-ray of sacroiliac joints as "usually appropriate" (rating 9) for initial evaluation 1.

Physical Examination Maneuvers

While no single test has strong validity alone, combined provocative testing improves diagnostic accuracy 2:

• Patrick's test (FABER test) 3
• Sacroiliac compression test 3
• Multiple provocation tests used together have better predictive value 2

Important caveat: Tenderness on palpation alone is insufficient for diagnosis 3.

Advanced Imaging (If Needed)

If radiographs are negative or equivocal and symptoms persist:

• CT without contrast (rating 7) can identify subtle erosions and degenerative changes, especially useful if MRI is contraindicated 1, 5
• MRI is NOT routinely indicated in this clinical scenario unless inflammatory disease is genuinely suspected, which it should not be given the patient's age and presentation 1

Diagnostic Injection

Sacroiliac joint injection with local anesthetic and corticosteroid serves both diagnostic and therapeutic purposes 2, 6:

• Considered the diagnostic gold standard for SI joint-mediated pain 2, 6
• Provides pain relief if the SI joint is the true pain generator 6, 3
• Must be interpreted cautiously due to potential false-positive and false-negative results 2

The American Society of Anesthesiologists and ASRA support SI joint injections for chronic SI joint pain 1.

Treatment Algorithm

First-Line Conservative Management

1. Continue NSAIDs (ibuprofen/Advil) as already providing benefit 1, 3

   • Monitor for GI toxicity given age; consider gastroprotective agents 1
   • Consider cardiovascular risk factors when selecting NSAIDs 1

2. Heat therapy (already effective) 3

3. Physical therapy addressing:

   • Posture and gait disturbances 2
   • Core strengthening and stabilization exercises 2

4. Consider adding acetaminophen for additional analgesia if NSAIDs alone insufficient 1

Second-Line Interventions

If conservative measures fail after 4-6 weeks:

Intra-articular SI joint injection with corticosteroid and local anesthetic holds the highest evidence rating (1 B+) 2, 3:

• Can provide both diagnostic confirmation and therapeutic relief 6, 3
• Effective for recalcitrant cases 3
• The American College of Rheumatology conditionally recommends local glucocorticoid injections for stable disease with active symptoms 1

Third-Line Options

For persistent pain despite injections:

• Cooled radiofrequency treatment of lateral branches S1-S3 (evidence rating 2 B+) 2
• Pulsed radiofrequency of L5 dorsal ramus and lateral branches S1-S3 if cooled RF unavailable (rating 2 C+) 2
• Conventional radiofrequency ablation may be considered for chronic SI joint pain 1

Critical Pitfalls to Avoid

• Do not pursue inflammatory workup (HLA-B27, inflammatory markers, MRI for sacroiliitis) in a 90-year-old with mechanical pain pattern—this represents inappropriate resource utilization 1
• Do not use systemic corticosteroids for axial/SI joint pain—no evidence supports this and carries significant risk in elderly patients 1
• Avoid peri-tendon injections near Achilles, patellar, and quadriceps tendons due to rupture risk 1
• Monitor NSAID toxicity carefully in elderly patients, particularly GI and cardiovascular risks 1