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Lumbricals of the foot

The lumbricals of the foot play a pivotal role, though they are often overshadowed by larger and more prominent muscles. They are located in the 2nd layer of the foot muscles.

Anatomy of the Lumbricals of the foot

The lumbricals of the foot are intrinsic muscles located within the sole, originating from the tendons of the flexor digitorum longus. Unlike their counterparts in the hand, the foot has four lumbrical muscles, each associated with the four lesser toes. The first lumbrical is unipennate and originates from the first tendon of the flexor digitorum longus, while the remaining three are bipennate, originating from the adjoining sides of the tendons destined for the second to fifth toes.

Each lumbrical muscle extends distally to insert into the medial aspect of the extensor expansion, a complex structure that extends over the dorsum of the toes. This unique insertion point is crucial for the lumbricals’ function, allowing them to exert influence over toe movement.

See Also: Foot Anatomy
Lumbricals muscles of the foot

Function of the Lumbricals

The primary function of the lumbricals of the foot is to facilitate flexion at the metatarsophalangeal (MTP) joints and extension at the interphalangeal (IP) joints. This action is essential for the smooth transition of the foot during the gait cycle, particularly during the toe-off phase, where efficient toe extension is necessary for propulsion.

Moreover, the Lumbricals of the foot contribute to the stabilization of the MTP joints by maintaining an optimal alignment of the toes during weight-bearing activities. Their action complements the balance and support provided by other foot muscles, ensuring a coordinated movement that is critical for activities such as walking, running, and jumping.

Clinical Significance

The lumbricals of the foot, despite their small size, are involved in various foot pathologies. Conditions such as hammertoe and claw toe deformities can arise from imbalances in the lumbrical muscle function, often exacerbated by factors like inappropriate footwear, muscle weakness, and systemic diseases like diabetes mellitus.

Understanding the anatomy and function of the lumbricals is crucial for healthcare professionals involved in the diagnosis and management of foot disorders. Therapeutic interventions, including physical therapy, orthotic devices, and, in some cases, surgical correction, often target the restoration of lumbrical function to alleviate symptoms and improve foot mechanics.

OriginFlexor digitorum longus tendon
InsertionExtensor digitorum longus tendon
InnervationMedial and lateral plantar nerve
Blood SupplyMedial and lateral plantar artery
ActionFlex metatarsophalangeal, extends interphalangeal

References & More

  1. Clinically Oriented Anatomy – 8th Edition
  2. Kara BA, Uzmansel D, Beger O. Innervation Patterns of the Lumbrical Muscles of the Foot in Human Fetuses. J Am Podiatr Med Assoc. 2020 May 1;110(3):Article_8. doi: 10.7547/17-132. PMID: 30649909. Pubmed
  3. Krishna H, Tandon R, Jacob TG. Degenerated lumbricals in the feet of adult human cadavers: case series. Anat Cell Biol. 2023 Jun 30;56(2):288-292. doi: 10.5115/acb.22.225. Epub 2023 Mar 10. PMID: 36894494; PMCID: PMC10319485. Pubmed
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