Muscles on the Bottom of the Foot:
| There are four layers of
muscles on the bottom of the foot. The
First Layer
the most superficial layer, which lies beneath a thick band of fibrous
connective tissue called fascia, has three muscles: On the medial side (the side the big toe is on), there's the Abductor Hallucis Muscle stabilizes the big toe by pulling it away from the second toe. The Flexor Digitorum Brevis Muscle lies in the central portion of the foot, and it helps pull the toes down, a motion called plantarflexion. On the outside (lateral portion) of the foot lies the Abductor Digiti Minimi Muscle. This muscle stabilizes the little toe by pulling it away from the fourth toe. |
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The Second Layer of
muscles consists of the Quadratus Plantae
Muscle, which attaches to and redirects
the pull of the Flexor Digitorum Longus tendon coming down from the leg.
This helps pull the four small toes down against the ground (plantarflexes
them). This layer also contains three small muscles called the Lumbricales. The lumbricale muscles actually have a somewhat complicated function for such small muscles. They help pull the toe down against the floor at the joint where the toes attach to the foot, yet help extend (or raise up) the toes at the next joint. Basically, they help balance the effects of the large muscles that pull the toes up and down. The word 'Lumbricale' means 'earthworm' in Latin, a reference to the small, narrow appearance of the muscle. |
| The Third Layer
of muscles has three more muscles: The Flexor Hallucis Brevis Muscle helps pull the big toe down (plantarflexes it) against the ground. The Ad helps stabilize the big toe by pulling it towards the second toe. (It counters the pull of the Abductor Hallucis Muscle described above.) This tendon is a deforming force in in many bunion deformities. The Flexor Digitorum Brevis Muscle pulls the four small toes down against the ground (plantarflexes them). |
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The Fourth Layer of muscles consists of four Dorsal Interosseous Muscles and three Plantar Interosseous Muscles. These seven muscles stabilize the small toes so they don't drift towards or away from the adjacent toes. |
Muscles on the Top of the Foot:
While the bottom of the foot has seventeen muscles, the top of the foot only has one.
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The Extensor Digitorum Brevis Muscle attaches to the top of the foot to help dorsiflex (lift up) the toes. It is pictured in the diagram to the left on the top of the foot.
Muscles that attach into the foot from the leg: In addition to the small muscles of the foot described above, there are quite a few muscles that attach into the foot from the leg. On the front or anterior portion of the leg is what's known as the Anterior Muscle Group. The Tibialis Anterior Muscle helps lift the foot against the ankle (Dorsiflexes it) and inverts it (pulls the sole of the foot so that it faces the opposite foot). The Extensor Hallucis Longus Muscle helps raise the big toe up (dorsiflexes it). The Extensor Digitorum Longus Muscle helps raise the small toes up (dorsiflexes them). This muscle may be involved in the "extensor substitution" variety of hammertoes. The Peroneus Tertius Muscle helps lift the foot against the ankle, and it everts it (pulls the sole of the foot so that it faces away from the opposite foot. |
| The muscles on the outside of
the leg is known as the Lateral Muscle Group.
It consists of two muscles, the Peroneus Longus and Peroneus Brevis Muscles. These muscles pull the foot down (plantarflexes it, like you'd push down on a pedal) and roll the foot in, as though you'd be standing more on your big toe joint. The Peroneus Longus also has the effect of stabilizing the first metatarsal bone, and when the pull of this muscle is abnormal because of a foot that has an arch that collapses too much, this muscle may play a role in the development of bunions. |
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The Posterior Muscle Group of the leg is divided into two sections.
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The superficial group consists of three muscles. The Gastrocnemius consists of two main muscle bellies, the medial and lateral heads of the muscle (see left). Beneath the gastrocnemius is the Soleus (see right) muscle. A small additional muscle, the Plantaris, runs next to the soleus muscle. These muscles come together near the foot to create the major tendon in the foot known as the calcaneal or Achilles tendon. We've devoted a web page to Achilles Tendon problems. This tendon pulls the foot down, like you'd move the foot if you pushed down on the gas pedal in your car.
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The Deep Group
of
muscles on the back of the calf, (lying beneath the gastrocnemius and
soleus muscles) consists of:
The Flexor Hallucis Longus Muscle pulls the big toe down against the ground (plantarflexes it). The Flexor Digitorum Longus Muscle, which splits into several small tendons that attach into the smaller toes to pull the small toes down against the ground (plantarflexes them). When the foot flattens more than it should, this muscle may be involved in the formation of "flexor stabilization" variety of hammertoes. The Posterior Tibial Muscle is the primary "supinator" of the foot, meaning it's the main muscle used when the foot pushes off in gait. We have a web page devoted to the problems associated with Posterior Tibial Tendon Dysfunction. |