Foot muscles – Layers and Compartments

Deep to the plantar fascia, muscles of plantar foot exist in 4 different layers. Extensor digitorum brevis makes dorsal layer of foot and remaining 18 muscles and 4 tendons make the 4 layers of plantar aspect or sole of foot.

In general:

  • Layer 1 and 3: 3 muscles each that contains intrinisc abductors, flexors and adductors
  • Layer 2 and 4: 2 muscles and 2 tendons that contains lumbricals and interossei

From superficial to deep, the layers are:

a. First layer

Mnemonic: Abs Flex Abs

  • Abductor hallucis
  • Flexor digitorum brevis (comparable to FDS of hand – both are superficial and insert into middle phalanx)
  • Abductor digiti minimii

b. Second layer

Mnemonic: Quadratus Lumborum OR you can also remember it with Flexor digitorum longus (comparable to FDP of hand – deeper and attaches to distal phalanx and the 2 muscles that attaches to FDL)

  • Quadratus plantae (Flexor digitorum accessorius)
  • Lumbricals (4)

Both of these muscles have attachment to the Flexor Digitorum Longus (FDL).

It also has 2 tendons of extrinsic muscles: Flexor digitorum longus (FDL) and Flexor hallucis longus (FHL).

It also has medial and lateral plantar nervers which are the terminal branches of tibial nerve.

c. Third layer

Mnemonic: Flex Add Flex (Opposite of first layer)

  • Flexor hallucis brevis
  • Adductor hallucis (like in hand, it has 2 heads – transverse and oblique)
  • Flexor digiti minimi

Both the flexor hallucis longus and brevis muscles have lateral origin, i.e. (distal fibula and cuboid/lateral cuneiform respectively) although they insert medially (towards great toe).

d. Fourth layer

Mnemonic: 4DAB and 3 PAD

  • 4 Dorsal interossei: ABduct MTP joint
  • 3 Plantar interossei: ADduct MTP joint
  • 2 tendons of extrinsic muscles: Peroneus longus and Tibialis posterior

9 compartments of foot

Please refer to an anatomy atlas and visualize for better understanding.

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