What is the cause of intermittent lateral right foot or ankle pain?

Intermittent Lateral Right Foot/Ankle Pain: Diagnostic Approach

Begin with plain ankle radiographs (AP, lateral, and mortise views) as the initial imaging study to evaluate for osseous abnormalities, and if normal with persistent symptoms, proceed to MRI for comprehensive soft tissue evaluation. 1

Initial Diagnostic Workup

Clinical History Focus

The intermittent nature and lateral location of your pain suggests several key differential diagnoses:

• Lateral ligament injury/instability (anterior talofibular or calcaneofibular ligament) - most common cause of lateral ankle pain 1
• Peroneal tendon pathology (tendinosis, tear, or subluxation) 1
• Lateral ankle impingement syndrome 1
• Osteochondral lesions of the talus 1
• Sinus tarsi syndrome 2

First-Line Imaging: Plain Radiographs

Obtain standard ankle radiographs (anteroposterior, lateral, and mortise views) as your initial study. 1

Radiographs can identify:

• Osseous abnormalities, fractures, or stress fractures 1
• Osteochondral defects (though 41% may be missed) 1
• Ossific fragments suggesting ligamentous injury or retinaculum avulsion 1
• Periostitis adjacent to tenosynovitis 1
• Degenerative changes 1

Important caveat: Radiographs are often initially normal in early tendon injuries, ligament tears, and cartilage-only osteochondral lesions. 1

If Radiographs Are Normal or Nonspecific

Suspected Lateral Ligament Instability

MRI is the preferred next study with 97% diagnostic accuracy for anterior talofibular ligament injury and 77-92% accuracy for chronic lateral ligament tears. 1

MRI advantages for ligament evaluation:

• Identifies exact injury location in 93% of cases 1
• Evaluates calcaneofibular ligament with 88-92% accuracy 1
• Detects associated injuries that mimic instability (tenosynovitis, tendon injury, osteochondral lesions) 1
• Assesses for synovitis and impingement 1

Alternative option: Ultrasound has 91% diagnostic accuracy for anterior talofibular ligament injury but only identifies exact location in 63% of cases, making it less reliable than MRI. 1

Suspected Peroneal Tendon Pathology

MRI demonstrates 83.9% sensitivity and 74.5% specificity for tendinopathy, and 54.5% sensitivity with 88.7% specificity for tendon tears. 1

Critical pitfall: Up to 34% of asymptomatic patients may have peroneus brevis tendon tears on MRI, so clinical correlation is essential. 1 MRI evidence of peroneal pathology has only 48% positive predictive value for clinical findings. 1

Ultrasound can be considered for dynamic assessment of peroneal tendon subluxation, though MRI has only 66% accuracy for detecting subluxation/dislocation. 1

Suspected Osteochondral Lesion

MRI performs similarly to arthroscopy with 96% sensitivity for osteochondral abnormalities, though it is less specific than CT. 1

MRI is particularly effective for:

• Determining lesion instability (97% sensitivity) 1
• Staging lesions preoperatively (81% accuracy) 1
• Detecting high signal deep to the lesion on T2-weighted images indicating instability 1

CT alternative: More specific (99%) but less sensitive than MRI for osteochondral lesions. 1 CT arthrography shows 90-92% accuracy for talar cartilaginous lesions versus 76-88% for MR arthrography. 1

Conservative Management While Awaiting Imaging

Based on location-specific patterns 2:

• For lateral pain suggesting ligament injury: Rest, activity modification, NSAIDs, ankle bracing/support 2
• For posterior/lateral pain suggesting tendinopathy: Open-backed shoes, heel lifts, NSAIDs, decreased activity, stretching exercises 2
• Avoid: Corticosteroid injections near tendons due to rupture risk 2, 3

When to Refer

Refer to orthopedic or podiatric foot and ankle specialist if: 2, 3

• No improvement after 6-8 weeks of appropriate conservative treatment
• Need for advanced imaging interpretation or diagnostic injection procedures
• Consideration of surgical intervention

Key Clinical Pearls

• The intermittent nature suggests mechanical instability or episodic impingement rather than constant inflammatory pathology 4
• Lateral ankle pain that "wraps around" suggests involvement of multiple structures (ligaments + tendons) requiring comprehensive MRI evaluation 1
• Do not rely on stress radiography alone - it has only 67% accuracy for anterior talofibular ligament injuries 1
• Symptoms improving in weeks to months occur in most patients, but 20-25% develop chronic or recurrent symptoms 4