Medial Head of Flexor Hallucis Brevis (Left) (Caput mediale musculi flexoris hallucis brevis)

Anatomy

The medial half of the short flexor of the great toe, a second-layer muscle straddling the first metatarsal with the long flexor tendon passing between the two heads. Its tendon carries the medial (tibial) sesamoid of the great toe and inserts on the medial base of the proximal phalanx. The two sesamoids it forms with the lateral head protect the long flexor tendon and carry the weight-bearing load of the first ray at push-off.

Origin & insertion

From the medial cuneiform and the first metatarsal base, to the medial base of the proximal phalanx of the great toe (with the tibial sesamoid in the tendon).

Action

Flexes the metatarsophalangeal joint of the great toe and steadies the medial sesamoid during push-off.

Innervation

Medial plantar nerve (S1–S2).

Clinical notes

The medial sesamoid in its tendon is the usual site of sesamoiditis and of bipartite sesamoid (a normal variant that must not be mistaken for a fracture). Turf-toe is a sprain of this muscle–sesamoid complex from forced dorsiflexion of the great toe on hard ground.

Related structures

• Medial cuneiform (left)
• First metatarsal (left)
• proximal phalanx of the big toe (left)

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