Third Plantar Interosseous (Left) (Musculus interosseus plantaris tertius)
Educational content only — not medical advice.
Anatomy
The most lateral plantar interosseous, arising from the base and medial side of the fifth metatarsal and inserting on the medial base of the proximal phalanx of the fifth toe. With its fellows it completes the PAD set that draws the lateral toes toward the second-toe axis.
Origin & insertion
From the base and medial side of the fifth metatarsal, to the medial base of the proximal phalanx of the fifth toe with the extensor hood.
Action
Adducts the fifth toe toward the second and flexes its metatarsophalangeal joint.
Innervation
Lateral plantar nerve (S2–S3).
Clinical notes
In the cavovarus foot of Charcot-Marie-Tooth disease the plantar interossei and the lateral sole muscles overpull against the weakened peronei, adding to the supinated, clawed deformity the surgeon must balance.
Related structures
Educational references
FAQ
What is the role of the Third Plantar Interosseous (Left)?
The most lateral plantar interosseous, arising from the base and medial side of the fifth metatarsal and inserting on the medial base of the proximal phalanx of the fifth toe. With its fellows it completes the PAD set that draws the lateral toes toward the second-toe axis.
Why is the Third Plantar Interosseous (Left) clinically important?
In the cavovarus foot of Charcot-Marie-Tooth disease the plantar interossei and the lateral sole muscles overpull against the weakened peronei, adding to the supinated, clawed deformity the surgeon must balance.
Source & license
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