Flexor Digitorum Longus Anatomy

Flexor Digitorum Longus Muscle

Origin: The posterior surface of the tibia and to the medial part of the fascia covering the tibialis posterior
Insertion: Plantar surfaces of the bases of the distal phalanges of the four lateral toes
Actions: Flexion of the four lateral toes
Innervation: Tibial nerve (L5,  S1, S2 )
Blood Supply: Posterior tibial artery

Primary Actions of the Flexor Digitorum Longus

1.  Flexion of the four lateral toes at the metatarsophalangeal joints

Agonists:

  • Flexor Digitorum Brevis
  • Flexor Digiti Minimi (fifth digit)

Antagonists:

  • Extensor Digitorum Longus
  • Extensor Digitorum Brevis

Lumbricals, dorsal interossei (second, third, and fourth digits), and plantar interossei (third, fourth, and fifth digits) assist with flexion of the toes at the metatarsophalangeal joints.

2.  Flexion of the four lateral toes at the proximal interphalangeal joints

Agonists:

  • Flexor Digitorum Brevis

Antagonists:

  • Extensor Digitorum Longus
  • Extensor Digitorum Brevis

3.  Flexion of the four lateral toes at the distal interphalangeal joints

Agonists:

  • None

Antagonists:

  • Extensor Digitorum Longus

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Secondary Actions of the Flexor Digitorum Longus

1. Assists with plantarflexion of the foot at the ankle
Agonists:

  • Gastrocnemius
  • Soleus

Antagonists:

  • Tibialis Anterior

Plantaris, tibialis posterior, peroneus longus, and flexor hallucis longus also assist with plantarflexion of the foot at the ankle.