What is the cause of pain at the base of the 4th metatarsal when putting pressure?

Pain at Base of 4th Metatarsal with Pressure

The most likely diagnosis is a stress fracture of the proximal 4th metatarsal, which requires immediate plain radiographs followed by MRI if x-rays are negative, as these injuries behave similarly to high-risk proximal 5th metatarsal fractures and can take 2-8 months to heal. 1

Primary Differential Diagnoses

The base of the 4th metatarsal is an uncommon but clinically significant site of injury that shares characteristics with proximal 5th metatarsal fractures:

• Stress fracture at the shaft-base junction is the leading concern, particularly if you are athletic or have increased forefoot loading, as these injuries are associated with forefoot adduction mechanisms and prolonged healing times 1
• Acute fracture should be considered if there was a specific traumatic event, though stress fractures can occur without obvious trauma 2
• Intermetatarsal bursitis between the 3rd and 4th metatarsals can cause localized pain that worsens with pressure 2, 3
• Osteoarthritis of the 4th metatarsophalangeal joint may present with pain at the base region, though typically affects the joint itself 2

Immediate Diagnostic Approach

Order weight-bearing plain radiographs of the foot (not ankle) as your first-line study, including anteroposterior, lateral, and oblique views. 2, 4

Key points about initial imaging:

• Radiographs have limited sensitivity (12-56%) for stress fractures early in their course, so a negative x-ray does not exclude the diagnosis 4
• Weight-bearing views are essential for proper evaluation of metatarsal alignment and pressure distribution 4, 5
• The Ottawa Ankle Rules guide whether radiographs are needed: obtain x-rays if there is palpation pain at the base of the metatarsal or inability to bear weight for four steps 2, 4

Advanced Imaging When Radiographs Are Negative

If radiographs are negative but clinical suspicion remains high, proceed directly to MRI of the foot without contrast. 2, 4

MRI is superior because:

• It has high sensitivity (87-93%) for detecting occult stress fractures and demonstrates bone marrow edema patterns that confirm early stress injuries 2
• MRI can detect stress fractures as early as bone scintigraphy but with greater specificity 2
• It provides prognostic information about healing time and can identify other soft tissue pathology simultaneously 2, 4
• Ultrasound can detect cortical irregularities but is operator-dependent and less reliable than MRI for metatarsal base injuries 2

Critical Clinical Features to Elicit

Obtain these specific details to refine your diagnosis:

• Point tenderness location: Direct palpation pain over the 4th metatarsal base strongly suggests fracture, while webspace tenderness suggests intermetatarsal pathology 4, 3
• Activity level: High-level athletic activity or recent increase in training intensity increases stress fracture risk 2
• Weight-bearing ability: Complete inability to bear weight suggests fracture or severe injury requiring urgent evaluation 2, 4
• Mechanism of injury: Forefoot adduction forces are specifically associated with proximal 4th metatarsal injuries 1
• Duration of symptoms: Gradual onset over weeks suggests stress fracture, while acute onset suggests traumatic fracture 2

Treatment Implications Based on Diagnosis

If stress fracture is confirmed:

• Expect prolonged healing of 2-8 months, significantly longer than typical metatarsal stress fractures which are usually more distal 1
• Initial treatment requires non-weight-bearing below-knee cast or boot immobilization for 3 weeks, followed by an additional 3+ weeks of weight-bearing immobilization 1
• Some patients remain symptomatic even after 3 months of rest and immobilization, similar to proximal 5th metatarsal injuries 1
• The proximal 2nd metatarsal is classified as a high-risk stress fracture site; the 4th metatarsal base behaves similarly and warrants aggressive conservative management 2

Critical Pitfalls to Avoid

• Do not rely solely on initial radiographs—they miss 44-88% of stress fractures early in the course; proceed to MRI if clinical suspicion is high despite negative x-rays 4
• Do not order ankle radiographs—they will not properly visualize the metatarsal bases or metatarsophalangeal joints 4
• Do not underestimate healing time—proximal 4th metatarsal injuries take considerably longer to heal than other lesser metatarsal fractures and require extended immobilization 1
• Do not miss infection in diabetic or immunocompromised patients, as these require urgent evaluation and possible surgical intervention 4