What is the cause and appropriate treatment for pain radiating from the right third toe up to the thigh?

Pain Radiating from Right Third Toe to Thigh

Immediate Diagnostic Priority: Lumbar Radiculopathy

This presentation of pain radiating from the toe proximally through the leg to the thigh strongly suggests lumbar radiculopathy (L5-S1 nerve root compression), which requires immediate subspecialist referral for evaluation including electromyography, nerve conduction velocity studies, and MRI. 1

The pattern of pain starting distally and radiating proximally is atypical for most musculoskeletal conditions and demands neurologic evaluation rather than assuming isolated foot pathology. 1

Clinical Assessment Algorithm

Key Examination Findings to Obtain

• Neurologic symptoms: Assess specifically for burning, tingling, numbness, or radiation patterns suggesting nerve involvement—these distinguish radiculopathy from mechanical foot pain. 1

• Straight leg raise test: Perform lumbar spine examination with straight leg raise and assess for neurologic deficits throughout the lower extremity to identify nerve root compression. 1

• Point tenderness mapping: Palpate the third toe, metatarsal shaft, dorsal foot along extensor tendons, lateral malleolus, posterior calcaneus, and along the posterior leg to localize pain generators. 2, 1

• Resisted dorsiflexion: Test for pain with resisted dorsiflexion of the foot and third toe to evaluate for extensor tendon inflammation. 3

• Calcaneal compression test: Squeeze the calcaneus medially to laterally to assess for stress fracture if heel involvement is suspected. 2, 1

Critical Diagnostic Imaging Sequence

• Weight-bearing radiographs of foot and ankle: Obtain initially for all patients with this presentation, though sensitivity for stress fractures is only 12-56%. 2, 3

• AP pelvis and lateral hip radiographs: Order if hip pathology contributes to symptoms based on examination. 1

• Lumbar spine MRI: This is the priority imaging study when radiculopathy is suspected based on examination findings showing radiation pattern, positive straight leg raise, or neurologic deficits. 1

• Advanced foot imaging if needed: If radiographs are negative but localized foot pain persists beyond 1 week, MRI without contrast or CT without contrast are equivalent alternatives for detecting stress fractures or soft tissue pathology. 2, 3

Differential Diagnoses to Consider

Primary Neurologic Causes (Most Likely)

• Lumbar radiculopathy: L5-S1 nerve root compression causes pain radiating from the heel proximally through the posterior leg and hip, matching this presentation. 1

• Deep peroneal nerve compression: Can cause dorsal foot pain with radiation, though typically does not extend to the thigh. 3

Local Foot Pathology (Less Likely Given Radiation Pattern)

• Extensor tendon inflammation: Causes pain over the dorsum of the foot worsening with active toe extension, but does not explain proximal radiation to thigh. 3

• Metatarsal stress fracture: Presents with dorsal foot pain and point tenderness over metatarsal shafts, but radiation to thigh is inconsistent with this diagnosis. 3

• Tarsometatarsal osteoarthritis: Causes dorsal foot pain worsening with weight-bearing and dorsiflexion, without typical proximal radiation. 3

Management Based on Diagnosis

If Radiculopathy Confirmed

• Immediate subspecialist referral: Neurologic heel pain with proximal radiation requires immediate referral for electromyography, nerve conduction studies, and MRI. 1

• Neuropathic pain medication: Consider pregabalin 75 mg twice daily initially, increasing to 150 mg twice daily (300 mg/day) within 1 week based on efficacy and tolerability, with maximum dose of 600 mg/day for neuropathic pain. 4

• Avoid NSAIDs as primary treatment: These do not address neuropathic pain mechanisms effectively in radiculopathy. 5

If Local Foot Pathology Identified

• For extensor tendonitis: Rest, activity modification, NSAIDs for pain and inflammation, and avoid corticosteroid injections near extensor tendons due to rupture risk. 2, 3

• For stress fracture: Protect and immobilize the foot, consider technetium bone scanning if radiographs negative but clinical suspicion high. 2, 1

Critical Pitfalls to Avoid

• Do not assume isolated plantar fasciitis or foot pathology: When pain radiates proximally beyond the heel to the thigh, this pattern demands neurologic evaluation rather than treating as mechanical foot pain. 1

• Do not rely solely on initial radiographs: Sensitivity for stress fractures ranges from only 12-56%, so negative X-rays do not exclude the diagnosis. 3

• Never diagnose based on imaging alone: Combine symptoms, clinical signs, and imaging findings to reach the correct diagnosis. 1

• Reexamine 3-5 days post-injury if initial examination limited: Excessive swelling and pain can obscure findings within the first 48 hours. 2

• Consider systemic causes: When symptoms are bilateral, involve other joints, or are unexplained by mechanical causes, consider arthritides, infections, tumors, or vascular compromise. 2, 1