What causes pain and swelling on the dorsal (top) portion of the foot without a history of trauma in a non-diabetic individual?

Pain and Swelling on Top of Foot Without Injury in Non-Diabetic Patient

Primary Diagnostic Considerations

In a non-diabetic patient with dorsal foot pain and swelling without trauma, the most likely causes include inflammatory conditions (gout, tendinitis), stress fracture, soft tissue infection/cellulitis, or less commonly, complex regional pain syndrome. 1

Immediate Clinical Assessment

Examine for these specific findings to narrow your differential:

• Check for signs of infection: Look for at least 2 of the following: local swelling/induration, erythema >0.5 cm, local tenderness, warmth, or purulent discharge 1, 2
• Palpate for point tenderness: Specifically assess the Achilles insertion, lateral malleolus, posterior superior calcaneus, lateral calcaneal wall, and dorsal metatarsals for stress fracture 2
• Perform calcaneal compression test: Medial-to-lateral squeeze to evaluate for stress fracture 2
• Assess for acute gout: Severe pain with acute onset, history of hyperuricemia, or prior attacks suggests this diagnosis 2
• Rule out deep venous thrombosis: Assess for unilateral leg swelling, calf tenderness, and consider D-dimer if clinically indicated 2

Diagnostic Algorithm

Start with plain radiographs of the foot to evaluate for fractures, bone lesions, or foreign bodies—this is the appropriate first imaging study. 1, 2

If radiographs are negative but clinical suspicion remains high:

• For suspected stress fracture with negative X-rays: Order technetium bone scan or MRI, as plain films may be normal in early stress fractures 2
• For suspected soft tissue infection or abscess: Ultrasound can identify fluid collections, periosteal thickening, and soft tissue abscesses 1
• For suspected osteomyelitis: MRI is the preferred modality with high sensitivity and specificity, and importantly, a negative MRI excludes osteomyelitis 1
• For suspected foreign body: Ultrasound is optimal for radiolucent material (plastic, wood), while CT is favored for radiodense bodies 1

Specific Conditions to Consider

Soft Tissue Infection/Cellulitis:

• Diagnose based on ≥2 inflammatory signs: erythema, warmth, swelling, tenderness, or purulent discharge 1, 2
• Exclude other inflammatory causes: trauma, gout, fracture, thrombosis, or venous stasis 1, 2

Stress Fracture:

• Common in dorsal metatarsals from repetitive loading or recent increase in activity 2
• Point tenderness over specific bones is highly suggestive 2
• Initial radiographs may be normal; advanced imaging needed if clinical suspicion high 2

Gout:

• Acute onset with severe pain is characteristic 2
• Can affect dorsal foot, not just the first MTP joint 2
• Joint aspiration showing urate crystals is diagnostic 1

Complex Regional Pain Syndrome (CRPS):

• Presents with swelling and pain, often following minor trauma that patient may not recall 3
• Plain X-rays may be normal initially 3
• MRI shows bone marrow edema in multiple bones with patchy, diffuse distribution 3

Critical Pitfalls to Avoid

• Do not assume absence of fever or elevated white blood cell count excludes infection—inflammatory markers may be absent in up to half of patients with significant infections 1
• Do not delay imaging if symptoms persist or worsen—early stress fractures and infections require prompt diagnosis 1, 2
• Do not overlook foreign bodies—glass fragments may be radiolucent and require ultrasound for detection 1

When to Refer or Escalate Care

• No improvement after 6-8 weeks of conservative treatment warrants subspecialist referral 2
• Suspected osteomyelitis requires infectious disease consultation and possible bone biopsy 1
• Recalcitrant cases may need surgical evaluation 2
• Suspected CRPS benefits from early pain management and physical therapy referral 3