Is ultrasound useful to confirm plantar fasciitis?

Ultrasound for Confirming Plantar Fasciitis

Yes, ultrasound is useful to confirm plantar fasciitis, demonstrating good diagnostic accuracy with 80% sensitivity and 88% specificity compared to MRI, though MRI remains the most sensitive imaging modality when diagnosis is uncertain. 1

Diagnostic Performance of Ultrasound

Ultrasound has established itself as a reliable imaging technique for plantar fasciitis diagnosis:

• Sensitivity and specificity of 80% and 88% respectively when compared to MRI as the reference standard 1
• Diagnostic accuracy ranges from 60-78% for specific findings including abnormal focal echogenicity (69%), edema around the plantar fascia (60%), and perifascial edema (78%) 1
• US elastography demonstrates even superior performance with 95% sensitivity and 100% specificity, making it a valuable advanced ultrasound technique 2

Key Sonographic Findings

When performing ultrasound for plantar fasciitis, look for:

• Increased plantar fascia thickness: >4mm is considered abnormal, with symptomatic patients typically showing 5.8mm compared to 2.4mm in healthy subjects 3, 4
• Hypoechoic appearance: Present in 68.3% of plantar fasciitis cases, indicating tissue degeneration 4
• Perifascial fluid accumulation: Supportive finding when present 1
• Abnormal focal echogenicity within the plantar fascia 1

Clinical Algorithm for Imaging

The American College of Radiology provides clear guidance on imaging approach 1, 2:

1. Initial evaluation: Weightbearing radiographs should be the first imaging study (85% sensitivity, 95% specificity for thickened plantar fascia and fat pad abnormalities) 2

2. When ultrasound is appropriate: Use ultrasound when there is high clinical suspicion and radiographs are negative or equivocal, particularly for confirming diagnosis and guiding therapeutic interventions 1, 5

3. When MRI is needed: Reserve MRI for cases that don't respond to initial treatment beyond 3 months or when diagnosis remains uncertain, as it is the most sensitive imaging study 2, 1

Practical Advantages of Ultrasound

Ultrasound offers several clinical benefits:

• Bedside availability: Can be performed rapidly at point-of-care 1
• Real-time correlation: Allows clinical correlation during examination, enabling dynamic assessment 1
• Treatment monitoring: Reliable for assessing plantar fascia thickness changes following interventions, with significant thickness reduction observable as early as 1 week post-treatment 3, 5
• Procedure guidance: Effective for guiding therapeutic injections safely 3, 5

Important Caveats

Correlation with clinical symptoms is essential: Some ultrasound findings can be present in asymptomatic patients, so imaging must always be interpreted in clinical context to avoid overdiagnosis 1

Differential diagnosis considerations: Ultrasound helps exclude other pathologies including calcaneal stress fractures, tarsal tunnel syndrome, and plantar fascia rupture 2

Diagnostic imaging is rarely needed initially: The diagnosis of plantar fasciitis is primarily clinical, based on history (heel pain with first steps in morning, pain after prolonged sitting) and physical examination (tenderness at medial plantar calcaneal region, pain with passive ankle/toe dorsiflexion) 6