The Painful Step: Common Pathologies of the Intrinsic Foot Muscles

Purpose or Learning Objective: To describe common intrinsic foot muscle pathologies and their etiologies.

Methods or Background: The intrinsic muscles of the foot are responsible for the fine motor actions of the foot and support the arches of the foot, formed by the tarsal and metatarsal bones, stabilized by ligaments and tendons. Failure of the intrinsic foot muscle may result in pain while walking.

Knowledge of normal anatomy, anatomical variants, and magnetic resonance imaging appearance of the intrinsic muscles of the foot and the corresponding innervation is essential to detect pathologies possibly related to the pain.

Results or Findings: This educational poster describes these pathologies:

• Denervation syndromes, characterized by abnormal T2 signal and/or caliber of the affected nerves and muscular denervation changes in the supplied muscles (acute: increased T2 signal; chronic: atrophy and fatty infiltration).

• Tarsal tunnel syndrome, caused by a compression of the tibial nerve/its branches in the tarsal tunnel due to space-occupying lesions, chronic trauma, or foot deformity.

• Baxter's neuropathy, caused by an impingement of the inferior calcaneal nerve, supplying the abductor digiti minimi, lateral half of the quadratus plantae, and flexor digitorum brevis. Entrapment can occur at the fascial edge of a hypertrophied abductor hallucis muscle, due to a course change at the medial edge of the quadratus plantae muscle and most commonly at the medial calcaneal tuberosity.

• Jogger's foot, commonly seen in runners and caused by compression of the medial plantar nerve, providing motor innervation to the abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, and first lumbrical muscles.

• Joplin's neuroma, involving perineural fibrosis of the medial plantar nerve, a mostly sensory nerve, but in its course runs off a muscular branch to the flexor hallucis brevis.

• Pseudotumors, more frequent in the foot than in other body parts and may include, for example, superficial fibromatoses, plantar varicosities, myositis ossificans, and foreign body granuloma.

Note: Tumors, trauma, exercise-induced changes, inflammation, metabolic disorders, and primary muscular diseases are mentioned but not described in detail.

Conclusion: Common pain-related pathologies of the intrinsic muscles of the foot include denervation syndromes, various entrapment or compression syndromes, as well as pseudotumors. Detailed knowledge of muscle anatomy, anatomical variants, and common pathologies is a prerequisite for a precise diagnosis.

Publication History

Article published online:
26 May 2023