What is the appropriate method to diagnose trochanteric bursitis in a patient presenting with hip pain and limited mobility?

Diagnosis of Trochanteric Bursitis

Obtain plain radiographs of the pelvis and hip first to rule out other causes of hip pain, then proceed to ultrasound as the primary diagnostic imaging modality to confirm trochanteric bursitis and evaluate associated soft tissue pathology. 1, 2

Initial Diagnostic Approach

Clinical Diagnosis

• The diagnosis is primarily clinical, based on lateral hip pain with characteristic tenderness over the greater trochanter. 3
• Recognize that true trochanteric bursitis frequently coexists with gluteus medius/minimus tendinopathy, making differentiation difficult. 4, 1
• Most cases actually result from gluteal muscle pathology rather than isolated bursal inflammation. 3

First-Line Imaging: Plain Radiographs

• Radiographs of the pelvis and hip should be obtained first to exclude other causes of hip pain such as osteoarthritis, fractures, or bone pathology. 5, 1
• Plain films can detect calcifications within the bursa but are not sensitive for diagnosing acute bursitis. 2

Confirmatory Imaging

Ultrasound (Preferred Initial Test)

• Ultrasound is the first-line diagnostic test for confirming trochanteric bursitis because it directly visualizes bursal fluid, inflammation, and calcifications. 2
• High-frequency ultrasound (≥10 MHz) is highly sensitive for detecting bursal pathology and can be performed at bedside. 2
• Ultrasound effectively detects trochanteric bursitis and differentiates it from other conditions, though distinguishing from gluteus medius tendinosis may be challenging. 1
• This modality can simultaneously evaluate the gluteal tendons for associated tendinopathy. 1

MRI (When Ultrasound is Equivocal or Symptoms Persist)

• MRI is appropriate when radiographs are negative or equivocal and there is suspicion for extra-articular soft tissue abnormalities. 5
• MRI comprehensively assesses peritrochanteric structures including the gluteus minimus and medius muscles, abductor tendons, and the trochanteric bursa. 1
• This modality is more sensitive than ultrasound for evaluating deep structures and detecting gluteus medius/minimus tears. 2
• MRI is highly sensitive and specific for detecting bursal fluid collections, distension, and capsular thickening. 2

Diagnostic Injection

Image-Guided Corticosteroid Injection

• Ultrasound-guided corticosteroid injection into the trochanteric bursa provides both diagnostic information and therapeutic benefit. 1
• Image guidance (ultrasound or fluoroscopy) ensures accurate needle placement and improves injection accuracy. 1, 2
• A positive response to injection helps confirm the diagnosis and exclude other pain sources. 5

Critical Pitfalls to Avoid

Common Diagnostic Errors

• Do not assume isolated bursitis: The two conditions (bursitis and gluteal tendinopathy) frequently coexist and may be difficult to distinguish. 4, 1
• In patients with hip prostheses: Be cautious not to misinterpret adverse reactions to metal debris (ARMD) as trochanteric bursitis, as extracapsular disease could mimic this condition. 1
• Ensure proper imaging sequence: Always obtain radiographs first before proceeding to advanced imaging to avoid missing alternative diagnoses. 1

When to Consider Aspiration

• Image-guided aspiration is indicated when septic bursitis is suspected to ensure accurate needle placement. 2
• Bursal fluid should be analyzed for Gram stain, culture, crystal analysis, cell count with differential, and glucose measurement. 2

Algorithmic Diagnostic Pathway

1. Clinical assessment: Lateral hip pain with trochanteric tenderness 3
2. Plain radiographs: Rule out bone pathology, detect calcifications 1, 2
3. Ultrasound: Confirm bursitis, evaluate gluteal tendons 1, 2
4. MRI (if needed): When ultrasound equivocal or symptoms persist despite treatment 1, 2
5. Diagnostic injection: Ultrasound-guided corticosteroid injection for confirmation and treatment 1