Third Plantar Interosseous Muscle

Origin

The third plantar interosseous muscle originates from the medial aspects of the base and body of the fifth metatarsal bone.

Insertion

The fibers of the third plantar interosseous muscle travel anteriorly to the little toe and insert, via a short tendon, onto the:

- medial aspect of the base of the proximal phalanx of little toe;

- extensor expansion of little toe.

Key Features & Anatomical Relations

The third plantar interosseous muscle is located in the fourth layer of muscles that are found in the plantar part of the foot. It is a short, unipennate skeletal muscle.

It is located:

- superior to the fourth lumbrical muscle of foot;

- inferior to the fourth dorsal interosseous muscle of foot;

- medial to the fifth metatarsal bone;

- lateral to the fourth metatarsal bone.

Actions

The third plantar interosseous muscle is involved in multiple actions:

- adducts the proximal phalanx of little toe (i.e., draws it towards the longitudinal axial line of the second toe) at the fifth metatarsophalangeal joint;

- simultaneously flexes the fifth metatarsophalangeal joint and extends the interphalangeal joints of the little toe (Standring, 2016).

List of Clinical Correlates

- Clawing of the toes

- Charcot-Marie-Tooth disease

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.

Actions

The third plantar interosseous muscle is involved in multiple actions:

- adducts the proximal phalanx of little toe (i.e., draws it towards the longitudinal axial line of the second toe) at the fifth metatarsophalangeal joint;

- simultaneously flexes the fifth metatarsophalangeal joint and extends the interphalangeal joints of the little toe (Standring, 2016).