What could be causing pain on the lateral side of my right foot after walking for 30 minutes, accompanied by intermittent swelling, that has been ongoing for 4 months without any prior injury?

Lateral Foot Pain After Walking: Most Likely Diagnosis

Based on your presentation of lateral right foot pain triggered by 30 minutes of walking, with intermittent swelling and no trauma history over 4 months, you most likely have peroneal tendinopathy or a lateral column stress injury (calcaneal stress fracture or fifth metatarsal stress fracture). 1, 2, 3

Key Diagnostic Considerations

Primary Differential Diagnoses

Peroneal tendinopathy is frequently misdiagnosed and leads to chronic lateral ankle pain and instability, presenting exactly as you describe—lateral foot pain with activity that improves with rest 2. The peroneus longus tendon courses along the lateral foot and can cause plantar lateral foot pain, particularly with walking 4.

Calcaneal stress fracture presents with progressively worsening pain following increased activity, with tenderness localizing to the lateral calcaneal wall 1. The calcaneal squeeze test (compression from medial to lateral) is highly suspicious for this diagnosis 1.

Fifth metatarsal stress fracture commonly causes lateral foot pain in the athletic population and can present insidiously without acute trauma 3.

Cuboid syndrome or calcaneocuboid joint pathology affects the lateral column and causes pain with weight-bearing activities 3.

Critical Physical Examination Findings You Need

Specific Palpation Points

• Lateral calcaneal wall tenderness (slightly posterior to subtalar joint) suggests calcaneal stress fracture 1
• Tenderness along peroneal tendons (behind lateral malleolus and along lateral foot) indicates peroneal tendinopathy 2, 4
• Fifth metatarsal shaft tenderness suggests stress fracture 3
• Cuboid region tenderness indicates cuboid pathology 3

Provocative Tests

• Calcaneal squeeze test: Compress heel from medial to lateral—pain suggests stress fracture 1
• Resisted eversion: Pain indicates peroneal tendinopathy 2
• Single stance heel rise with varus inversion stress: Localizes peroneus longus pathology 4

Imaging Strategy

Initial Approach

Start with weight-bearing radiographs of the foot and ankle 1. However, recognize that initial X-rays have poor sensitivity (12-56%) for stress fractures, so negative films do not exclude the diagnosis 5.

If Radiographs Are Negative

If pain persists beyond 1 week with negative X-rays, obtain MRI without contrast or CT without contrast—these are equivalent alternatives for detecting stress fractures 1, 5. Symptoms of stress fractures often precede radiographic findings by weeks 1.

Technetium bone scanning is an alternative if MRI/CT unavailable 1.

Treatment Algorithm Based on Diagnosis

For Peroneal Tendinopathy

• Relative rest and activity modification (reduce walking duration initially) 2
• Physical therapy focusing on eccentric strengthening and proprioception 2
• Orthotics or lateral heel wedge to reduce peroneal tendon stress 2
• Close monitoring for surgical indications if conservative treatment fails 2

For Calcaneal Stress Fracture

• Protect and immobilize the foot with walking boot or cast 1
• Non-weight-bearing or protected weight-bearing for 6-8 weeks 1
• Gradual return to activity only after pain-free weight-bearing 1

For Fifth Metatarsal Stress Fracture

• Immobilization in walking boot 3
• Non-weight-bearing if proximal metaphyseal-diaphyseal junction involved (Jones fracture zone—high nonunion risk) 3

Critical Pitfalls to Avoid

Do not rely on initial radiographs alone—stress fractures are frequently missed on first X-rays, and symptoms precede radiographic changes by weeks 1, 5. Your 4-month duration makes stress fracture less likely unless you've continued activity despite pain.

Peroneal tendinopathy is commonly misdiagnosed—if you have chronic lateral foot pain without clear fracture, this diagnosis must be actively considered 2.

Avoid corticosteroid injections near tendons—particularly the peroneal and Achilles tendons, as this risks tendon rupture 1.

When to Refer to Podiatric Foot and Ankle Surgeon

• No improvement after 6-8 weeks of appropriate conservative treatment 6, 1
• Need for advanced imaging (MRI, bone scan) if not already obtained 1
• Suspected stress fracture requiring immobilization 1
• Consideration of surgical intervention for refractory tendinopathy 2

What You Should Do Now

Schedule evaluation with your primary care physician or podiatrist within 1-2 weeks for physical examination focusing on the specific palpation points and provocative tests described above 1. Request weight-bearing foot and ankle radiographs at that visit 1. Given your 4-month symptom duration without improvement, you likely need advanced imaging (MRI) regardless of X-ray findings 1, 5.