Differential Diagnosis for Foot Pain: A Comprehensive Guide

Foot pain is a common complaint with a wide range of potential causes, making accurate diagnosis crucial for effective management. A systematic approach, incorporating patient history, physical examination, and judicious use of imaging, is essential to arrive at the correct differential diagnosis. This guide provides a structured overview to aid in the differential diagnosis of foot pain.

History

A thorough history is paramount in narrowing down the potential causes of foot pain. Key questions to ask the patient include:

• Pain Characteristics: Inquire about the nature of the pain (sharp, dull, burning, throbbing), its onset (sudden or gradual), precise location, duration (constant or intermittent), and factors that exacerbate or relieve the pain. Assess the severity and frequency of pain episodes, and whether there has been any progression of symptoms. It’s also important to determine if there have been prior episodes of foot pain.
• Antecedent Events: Explore any history of trauma or specific injury mechanism. Investigate changes in activity level, including new exercises or increased intensity. Inquire about specific activities that trigger pain, such as running or prolonged standing, and the type of footwear typically worn.
• Red Flags: Specifically ask about nighttime pain, which can be a red flag suggesting more serious underlying conditions such as infection, bone tumors, or neuropathy.

Evaluation

A comprehensive physical examination is critical in evaluating foot pain. This includes both inspection and palpation, and should be complemented by imaging when clinically indicated.

Examination

• Inspection:

  • Visually assess the foot for any deformities, nodules, swelling, calluses, or corns.
  • With the patient standing, evaluate for pes planus (flatfoot). Observe if the medial plantar surface of the foot makes contact with the floor, which is indicative of flatfoot.

• Palpation: Systematically palpate the following areas using your thumbs to identify areas of tenderness:

  • Heel: Palpate the posterior and inferior calcaneus, plantar fascia, and Achilles tendon to assess for tenderness, nodules, or thickening.
  • Midfoot/Forefoot: Palpate the heads of the metatarsals and the grooves between them. Perform a forefoot compression test by squeezing the forefoot between your thumb and fingers just proximal to the heads of the 1st and 5th metatarsals, noting any elicited pain.

Imaging

Radiographic imaging is not always necessary but is guided by clinical findings, particularly when considering fractures.

• Ottawa Ankle Rules: Utilize the Ottawa Ankle Rules, a validated clinical prediction tool with high sensitivity (99%) for detecting fractures as a cause of ankle and foot pain. This tool helps to minimize unnecessary radiographs.

  Obtain a foot x-ray series only if there is pain in the midfoot AND either of the following:
  – Inability to bear weight both immediately after injury and in the emergency department/clinic (four steps)
  – Bony tenderness at the navicular bone or the base of the fifth metatarsal

  • If radiographs are indicated based on the Ottawa Ankle Rules or clinical suspicion, obtain anteroposterior (AP), lateral, and oblique views of the foot to adequately visualize potential fractures and other bony abnormalities.

Differential Diagnosis

Based on the history, physical exam, and imaging when appropriate, consider the following differential diagnoses for foot pain:

Plantar Fasciitis

• Description: Plantar fasciitis is the most frequent cause of heel pain in outpatient settings. It commonly affects individuals who run, especially when increasing training intensity or changing footwear, those who stand for extended periods, people with high arches or tight Achilles tendons, and individuals with obesity.
• History: Patients typically describe severe, burning, or lancinating pain located on the bottom of the foot, specifically at the arch or inferior heel. Characteristically, the pain is most intense in the morning upon waking or after periods of inactivity and may lessen with initial walking, only to potentially return later in the day or after prolonged activity.
• Exam: Palpation over the plantar fascia’s insertion point on the calcaneus (anteromedial heel) will elicit significant tenderness. Pain is further accentuated when the examiner dorsiflexes the patient’s foot while palpating the plantar fascia. Radiographs are generally not helpful in diagnosing plantar fasciitis and while heel spurs may be visible, they are not considered a primary source of pain in this condition.
• Differential: Consider calcaneal stress fracture, nerve entrapment, neuroma, and heel pad syndrome in the differential diagnosis.
• Treatment: Initial management focuses on reducing inflammation and pain. Rest is paramount, and patients should be advised to reduce weight-bearing activities for several days. Conservative treatment includes stretching exercises for the plantar fascia and Achilles tendon, strengthening exercises for foot muscles, ice application, massage, and nonsteroidal anti-inflammatory drugs (NSAIDs) as first-line pain relief. Arch supports can help unload the plantar fascia, and heel cups provide cushioning. Nighttime splints to maintain the ankle in a 90-degree position and arch taping can also be beneficial. Weight loss is recommended for obese patients. Corticosteroid injections can be considered, using a 25-gauge or smaller needle into the most tender area, limiting the injection volume to 1.5 ml to minimize discomfort and the risk of fascial rupture or fat pad atrophy. Most cases (around 80%) resolve within a year with conservative management. Referral to a foot and ankle specialist is recommended if symptoms are refractory to conservative treatment, or if nighttime pain is persistent. Extracorporeal shock wave therapy or plantar fasciotomy may be considered in recalcitrant cases.

Hallux Valgus Deformity (Bunion)

• Description: Hallux valgus, commonly known as a bunion, is characterized by the lateral deviation of the first toe at the metatarsophalangeal (MTP) joint. It’s a prevalent condition, particularly among women. Diagnosis is typically straightforward based on physical examination. Radiographs are generally not required for diagnosis but can be obtained to evaluate the extent of any articular damage to the 1st MTP joint.
• Differential: Differential diagnoses include concomitant bursitis (inflammation of the bursa at the medial aspect of the bunion, often exacerbated by tight footwear), and osteoarthritis of the MTP joint. Gout and septic arthritis of the MTP joint should also be considered, especially in cases of acute onset pain and inflammation.
• Treatment: Evidence supporting conservative management is limited, but expert recommendations include initial measures such as shoe modifications (wearing wider, low-heeled shoes), orthotics to support foot alignment, nighttime splinting to gently correct alignment, medial bunion pads to reduce friction, ice application after activity, and acetaminophen or NSAIDs for pain relief. Surgical referral is considered based on the severity of the patient’s symptoms, the degree of deformity, and the lack of improvement with conservative treatments.

Interdigital (Morton’s) Neuroma

• Description: Morton’s neuroma is a painful condition resulting from the entrapment of an interdigital nerve, most commonly affecting the nerve between the 3rd and 4th toes. It less frequently occurs between the 2nd and 3rd or 4th and 5th toes. Women are affected more often than men (8:1 ratio). Risk factors include overpronation and wearing high-heeled shoes, particularly those with pointed and narrow toe boxes, which compress the forefoot and shift weight forward.
• History: Patients classically describe burning pain or numbness during weight-bearing, radiating distally from the base of the affected toes, often described as “walking on a pebble.” Other symptoms may include cramping or progressive sharp, shooting pain in the ball of the foot or between the toes.
• Exam: Tenderness is elicited upon direct palpation in the interspace between the affected metatarsal heads, especially when the foot is compressed mediolaterally. Compression alone may reproduce the pain. The “Metatarsal Shift Test” involves reproducing pain by holding the metatarsal heads of two adjacent toes and moving them in opposite directions. Mulder’s sign, a palpable and sometimes audible click when palpating the interspace while squeezing the metatarsal joints, may also be present. Plain radiographs are typically obtained to rule out stress fractures, especially if symptoms have been present for 10-14 days. Conservative treatment is usually initiated before considering MRI, as MRI can show neuromas in asymptomatic individuals.
• Differential: Differential diagnoses include synovitis, capsulitis, plantar fat pad atrophy, metatarsal stress fracture, and avascular necrosis.
• Treatment: Symptoms often resolve within weeks by avoiding high-heeled, pointed-toe shoes and switching to low-heeled shoes with a wide toe box. Bilateral shoe inserts or metatarsal pads placed proximal to the metatarsal heads can also be beneficial. NSAIDs are generally not very effective. Corticosteroid and anesthetic injections can be considered if the diagnosis is highly certain. Surgical referral is indicated if symptoms do not improve with 9-12 months of conservative measures, in cases of very severe pain, or a protracted clinical course.

Metatarsalgia

• Description: Metatarsalgia is a general term for pain in the ball of the foot. It is frequently caused by repetitive activities like running or wearing ill-fitting shoes that place excessive pressure on the metatarsal heads.
• Diagnosis: Symptoms may overlap with interdigital neuroma, but on examination, tenderness is typically located just proximal to the metatarsal heads, rather than in the interdigital space. Radiographs are recommended to rule out stress fractures.
• Treatment: Treatment primarily involves metatarsal pads placed proximal to the area of tenderness to redistribute weight and reduce pressure on the metatarsal heads.

Acute Metatarsal Fractures

• Description: Acute metatarsal fractures usually result from direct axial blows to the foot (common for shaft fractures) or twisting forces (more common for proximal fifth metatarsal fractures). Initial assessment must prioritize identifying conditions requiring immediate referral, such as neurovascular compromise or open fractures.
• History: Patients present with pain, swelling, significant ecchymosis, and difficulty walking. Consider early compartment syndrome if the pain is disproportionate to the apparent injury.
• Exam: Perform a thorough neurovascular examination, including assessment of capillary refill, distal pulses, and sensation. Inspect for open wounds, devitalized skin, or tenting of skin over a displaced fracture. Palpate for point tenderness along the metatarsals. Radiographs, including AP, lateral, and oblique views, are essential to confirm the diagnosis and classify the fracture pattern.
• Treatment: Treatment depends on the specific type and location of the fracture.
  • Non-emergent, but prompt referral is required for: Intra-articular or displaced fractures (>3 mm displacement), multiple fractures, fracture-dislocations, significant angulation (>10 degrees), fractures of the 1st metatarsal, “Jones Fracture” (fracture of the diaphysis of the fifth metatarsal, particularly in active individuals due to risks of delayed healing and non-union), or Lisfranc injuries (discussed below).
  • Conservative treatment is appropriate for non-displaced fractures:
    • Metatarsal shaft fractures (2nd-5th): Treat with a posterior splint, non-weight bearing, and follow-up within 3-5 days. Healing time is approximately 6 weeks.
    • 5th metatarsal tuberosity avulsion fracture: Treat with a compressive dressing, weight-bearing and range of motion as tolerated, and follow-up in 4-7 days. Healing time is typically 4-8 weeks.
    • Follow-up appointments for all fracture types:
      • At 1 week: Repeat radiographs to ensure maintenance of alignment. If alignment is unchanged, transition to a short leg walking boot, with progressive weight-bearing and physical therapy.
      • At 4-6 weeks: Repeat radiographs to assess for alignment and healing (evidence of callus formation). If radiographic healing is evident and point tenderness has resolved, foot protection can be discontinued.

Metatarsal Shaft Stress Fractures

• History: Stress fractures of the metatarsal shafts typically occur in the context of a sudden increase in activity level or chronic overuse and overload.
• Exam: Examination reveals point tenderness directly over the fracture site and pain at the fracture site with axial loading of the metatarsal head. Stress fractures are often not visible on plain radiographs until symptoms have been present for 2-6 weeks. MRI is generally not necessary if clinical suspicion is high. Presumptive treatment can be initiated based on clinical findings.
• Treatment: Metatarsal shaft stress fractures are managed with rest and avoidance of the inciting activity for 4-8 weeks. Immobilization is typically not required. If pain is significant, partial weight-bearing with crutches may be used for a short period.

Tarsal Tunnel Syndrome

• Description: Tarsal tunnel syndrome is caused by entrapment of the posterior tibial nerve as it passes through the tarsal tunnel, located behind the medial malleolus. Common causes include trauma or fracture, space-occupying lesions within the tarsal tunnel, systemic diseases like rheumatoid arthritis (RA), and biomechanical abnormalities that compress the nerve.
• History: Patients report numbness, paresthesias, and burning pain in the posteromedial ankle and heel, which may radiate into the distal foot and toes. A history of foot trauma is frequently present. Symptoms are typically exacerbated by activity and relieved by rest.
• Exam: Percussion over the path of the posterior tibial nerve posterior to the medial malleolus elicits symptoms (Tinel’s sign). Provocative maneuvers include the dorsiflexion-eversion test and plantar flexion-inversion test, which may reproduce symptoms. Sensory loss in the distribution of the tibial nerve may be present, although motor deficits are less common. MRI is the preferred imaging modality to evaluate for space-occupying lesions or nerve compression. EMG and ultrasound can also be considered in certain situations.
• Treatment: Conservative management includes NSAIDs, activity modification to reduce nerve irritation, and shoe modifications or orthotics to correct biomechanical factors. If conservative measures fail, corticosteroid injections into the tarsal tunnel or neuromodulator medications may be considered. Surgical decompression of the tarsal tunnel is an option if conservative therapy is unsuccessful.

Lisfranc Fracture (Injury)

• Description: A Lisfranc injury involves disruption of the Lisfranc ligament complex, which stabilizes the midfoot. The base of the 2nd metatarsal is “keystoned” between the 1st and 3rd metatarsal bases and cuneiform bones. Lisfranc injuries typically result from axial loading forces applied to the foot, leading to rupture of the ligamentous structures that maintain the 2nd metatarsal base in its anatomical position.
• History: Patients report midfoot pain following an axial load injury, such as a fall from height or a sports-related twisting injury.
• Exam: Plantar ecchymosis in the midfoot region is a highly suggestive sign of a Lisfranc injury. Common examination findings include point tenderness in the midfoot and pain elicited by twisting the forefoot while stabilizing the calcaneus. A thorough neurovascular examination is crucial as Lisfranc injuries can compromise the dorsalis pedis artery. Weight-bearing AP radiographs are essential for diagnosis, as non-weight-bearing films may underestimate the extent of injury.
• Treatment: Lisfranc injuries require prompt orthopedic referral. Treatment options range from casting to surgical internal fixation, depending on the severity and type of injury.

Charcot Arthropathy of the Foot or Ankle

• History: Charcot arthropathy should be suspected in patients with peripheral neuropathy, most commonly due to diabetes mellitus, who present with a relatively painless but significantly swollen foot. Patients may report warmth, redness, and swelling with minimal pain.
• Exam: Examination findings include intact peripheral pulses, hyperemia, erythema, warmth, and occasionally joint crepitus. Plain radiographs may initially be normal or show osteopenia. MRI or bone scans may be necessary to differentiate Charcot arthropathy from osteomyelitis, as findings can be similar.
• Differential: Key differential diagnoses include cellulitis, osteomyelitis, and gout. Charcot arthropathy should be considered in any patient with peripheral neuropathy and a red, hot, swollen foot.
• Treatment: Failure to promptly recognize and manage Charcot arthropathy can lead to progressive joint destruction and the development of a rocker-bottom foot deformity if weight-bearing is continued on the affected foot. Strict non-weight-bearing is mandatory, and urgent referral to a foot and ankle specialist for definitive management is essential. Antibiotics may be initiated if infection cannot be definitively ruled out.

References

Ahn JM, El-Khoury GY. Occult Fractures of Extremities. Radiologic Clinics of North America. 2007;45(3):561–579.

Bica D, Sprouse RA, and Armen J. Diagnosis and Management of Common Foot Fractures. Am Fam Physician. 2016. 93(3): 183-191.

Goff J, Crawford R. Diagnosis and Treatment of Plantar Fasciitis. Am Fam Physician. 2011;84(6):676–682.

Tu, P. Heel Pain: Diagnosis and Management. Am Fam Physician. 2018 Jan 15;97(2):86-93.

Gould J. Tarsal Tunnel Syndrome. Foot and Ankle Clinics of North America. 2011;16(2):275–86.

Page N and Nouvong A. The Top 10 Things Foot and Ankle Specialists Wish Every Primary Care Physician Knew. MayClin Proc. June 2006;81(6):818-822.

Tu, P. Heel Pain: Diagnosis and Management. Am Family Physician 2018; 97(2): 86-93.