What are the diagnostic criteria and methods for plantar fasciitis?

Diagnostic Criteria and Methods for Plantar Fasciitis

MRI is currently considered the most sensitive imaging study for diagnosing plantar fasciitis, though clinical diagnosis based on history and physical examination remains the primary approach. 1

Clinical Diagnostic Criteria

The diagnosis of plantar fasciitis is primarily clinical, with several key findings:

• Stabbing, non-radiating pain in the proximal medioplantar surface of the foot, typically worst with first steps in the morning or after prolonged sitting 2, 3
• Pain that becomes worse at the end of the day after prolonged standing 3
• Point tenderness to palpation at the proximal plantar fascial insertion on the anteromedial calcaneus 3, 4
• Discomfort in the proximal plantar fascia elicited by passive ankle/first toe dorsiflexion 2

Imaging Methods

When clinical diagnosis is uncertain or symptoms persist beyond 3 months despite treatment, imaging may be indicated:

Initial Imaging

• Radiographs should be the initial imaging study for painful heel, though they are typically insensitive for diagnosing plantar fasciitis 1
• Weightbearing radiographs showing thickened plantar fascia and fat pad abnormalities have 85% sensitivity and 95% specificity for plantar fasciitis 1

Advanced Imaging

• MRI: Currently considered the most sensitive imaging study for plantar fasciitis diagnosis 1

  • Allows accurate characterization of the plantar fascia and adjacent soft tissues/bones 1
  • Findings include increased plantar fascia thickness and abnormal tissue signal 2
  • MRI findings must be correlated with clinical symptoms to avoid overcalling plantar fasciitis, as some findings can be seen in asymptomatic patients 1

• Ultrasound (US):

  • Good sensitivity (80%) and specificity (88%) compared to MRI 1
  • Diagnostic accuracy findings using MRI as reference standard 1:
    • 69% for abnormal focal echogenicity within plantar fascia
    • 60% for edema around plantar fascia
    • 78% for perifascial edema
    • 69% for rupture of plantar fascia
    • 56% for associated calcaneal spur
  • US elastography shows higher sensitivity (95%) and specificity (100%) than conventional US (66% and 75%) 1
  • Some authors consider US superior to MRI in differentiating true fiber interruption/tearing from edema 1
  • Reasonable and inexpensive diagnostic tool for patients with persistent pain beyond 3 months 3

• Bone Scan with SPECT or SPECT/CT:

  • Can be useful with increased specificity compared to bone scintigraphy alone 1
  • A characteristic pattern on 3-phase bone scintigraphy helps differentiate plantar fasciitis from calcaneal stress/avulsion fractures 1
  • Despite advantages, MRI and high-frequency US remain the most frequently used imaging modalities for heel pain 1

Diagnostic Algorithm

1. Begin with clinical assessment focusing on:

   • Location and timing of pain (medial heel pain worst in morning) 2, 3
   • Point tenderness at plantar fascia origin 4
   • Pain exacerbation with toe dorsiflexion 2

2. If diagnosis is unclear or symptoms persist beyond 3 months:

   • Obtain weightbearing radiographs to exclude other pathologies 1
   • Proceed to ultrasound if readily available (cost-effective option) 3
   • Consider MRI for definitive evaluation when diagnosis remains uncertain 1

Common Pitfalls and Caveats

• Plantar fasciitis is a diagnosis of exclusion; other mechanical, rheumatologic, and neurologic causes must be considered first 5
• MRI findings should always be correlated with clinical symptoms to avoid overcalling plantar fasciitis, as some findings can be seen in asymptomatic patients 1
• Diagnostic imaging is rarely needed for initial diagnosis of plantar fasciitis and should be reserved for recalcitrant cases or to rule out other heel pathology 2
• The term "plantar fasciopathy" may be more appropriate as the condition is not primarily inflammatory 3
• Ninety percent of patients will improve with conservative treatments within 12 months 2, 3