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Second Lumbrical of the Foot

musculus lumbricalis secundus pedis

The second lumbrical is bipennate, arising from adjacent FDL tendon slips. It is innervated by the lateral plantar nerve, unlike the first lumbrical. It stabilises the third MTP joint and maintains the intrinsic-plus position of the third toe during the propulsive phase of gait.

Nerve: Lateral plantar nerve (deep branch, S2, S3) Blood Supply: Second plantar metatarsal artery Region: Foot & Ankle

Anatomical Data

Origin, Insertion & Supply

Origin	Adjacent borders of the first and second FDL tendon slips (bipennate)
Insertion	Medial base of the proximal phalanx of the third toe and extensor hood
Nerve Supply	Lateral plantar nerve (deep branch, S2, S3)
Blood Supply	Second plantar metatarsal artery

Biomechanics

Function & Actions

Actions	Flexes the MTP joint of the third toe; Extends the PIP and DIP joints of the third toe

Clinical Relevance

Clinical Notes

The lateral plantar nerve innervation of the second through fourth lumbricals means that complete lateral plantar nerve injury produces claw toes at the third through fifth toes with relative preservation of the second toe (first lumbrical medial plantar territory). This pattern helps distinguish complete plantar nerve injury from intrinsic muscle disease.

Palpation

Not directly palpable. Assessed by third MTP flexion with IP extension resistance testing.

Pathology

Common Injuries & Conditions

Third Toe Claw from Lateral Plantar Neuropathy

Claw deformity at the third toe from second lumbrical denervation in lateral plantar nerve injury, with preservation of second toe intrinsic function from intact medial plantar supply.