What is the differential diagnosis for severe right metatarsal pain that prevents walking?

Differential Diagnosis for Severe Right Metatarsal Pain Preventing Walking

The most likely diagnoses for severe metatarsal pain preventing ambulation are stress fracture, Morton's neuroma, plantar plate tear with adjacent pseudoneuroma, or subchondral injury—all of which require immediate plain radiographs as the initial diagnostic step. 1, 2

Primary Differential Diagnoses

Osseous Pathology

• Stress fracture is a leading cause of severe metatarsal pain that prevents walking, though initial radiographs have limited sensitivity (12-56%) and may appear normal early in the course 1
• Acute fracture of the fifth metatarsal base is particularly common given the prominent tuberosity at this location 3
• Subchondral injury at the metatarsal heads can cause severe pain and is frequently missed on initial imaging 2
• Freiberg's infraction (osteochondrosis of the metatarsal head, typically second metatarsal) should be considered, especially in adolescents 1

Soft Tissue Pathology

• Morton's neuroma (interdigital neuroma) is one of the most common causes of metatarsalgia, typically occurring between the third and fourth metatarsals 4, 2
• Plantar plate tear with adjacent pseudoneuroma frequently causes severe forefoot pain and is a common diagnosis in practice 2
• Intermetatarsal bursitis can mimic neuroma symptoms 1

Inflammatory/Degenerative Conditions

• Osteoarthritis of the metatarsophalangeal (MTP) joints can cause severe pain, particularly at the first MTP joint 1
• Sesamoiditis or sesamoid fracture at the first metatarsal should be considered if pain is localized to the great toe 1
• Capsulitis of the MTP joints, representing inflammation of the joint capsule 5, 6

Systemic/Metabolic Causes

• Gout or other crystalline arthropathy, particularly if there is acute onset with erythema and swelling 5
• Infection (osteomyelitis or septic arthritis) must be ruled out if there are systemic symptoms, diabetes, or immunocompromise 4

Immediate Diagnostic Approach

Initial Imaging

Order weight-bearing plain radiographs of the foot (not ankle) as the first-line imaging study, including lateral and oblique views. 1, 7

• Radiographs can identify fractures, dislocations, osteoarthritis, and bony deformities with good specificity (88-96% for stress fractures) 1
• The Ottawa Ankle Rules should guide whether radiographs are needed: obtain x-rays if there is palpation pain at the base of the fifth metatarsal or navicular bone, or inability to bear weight for four steps 1, 3
• Weight-bearing views are essential for proper evaluation of foot structures and pressure distribution 1, 7

Advanced Imaging When Radiographs Are Negative

If radiographs are negative but clinical suspicion remains high for stress fracture or soft tissue pathology, proceed directly to MRI of the foot without contrast. 1, 4, 7

• MRI has high sensitivity (87-93%) and specificity (68-100%) for Morton's neuroma 4
• MRI is superior to ultrasound for detecting plantar plate tears 4
• MRI is the examination of choice for occult stress fractures and subchondral injury 7, 2
• Ultrasound can be used as an alternative for Morton's neuroma (sensitivity 83-96%) but is operator-dependent 4

Key Clinical Features to Elicit

History

• Mechanism of injury: sudden trauma suggests fracture; insidious onset suggests stress fracture, neuroma, or degenerative pathology 2, 5
• Location of pain: pain between metatarsal heads suggests neuroma; pain directly under metatarsal heads suggests plantar plate tear or metatarsalgia 2, 6
• Activity level: high-level athletic activity increases risk of stress fracture 1
• Footwear: tight or high-heeled shoes predispose to Morton's neuroma 4

Physical Examination

• Palpation: point tenderness over metatarsal shaft suggests fracture; tenderness in webspace suggests neuroma 1, 2
• Weight-bearing ability: complete inability to bear weight suggests fracture or severe soft tissue injury 1
• Swelling and erythema: suggests acute fracture, gout, or infection 5
• Mulder's click: palpable click with compression of metatarsal heads suggests Morton's neuroma 4
• Drawer test: instability of MTP joint suggests plantar plate tear 2

Critical Pitfalls to Avoid

• Do not rely solely on initial radiographs for stress fractures—they miss 44-88% of cases early in the course; proceed to MRI if clinical suspicion is high 1, 7
• Do not order ankle radiographs for metatarsal pain—they will not properly visualize the metatarsals or MTP joints 7
• Do not assume all forefoot pain is "metatarsalgia"—this is a symptom, not a diagnosis; identify the specific underlying pathology 2, 5, 8
• Do not miss infection in diabetic or immunocompromised patients—these patients require urgent evaluation and may need surgical intervention 4