The flexor digiti minimi brevis of the foot flexes the little toe at the MTP joint and provides minimal lateral arch support. Analogous to its hand counterpart, it is the central hypothenar muscle of the foot alongside the ADM and opponens. Its origin from the fifth metatarsal base makes it relevant to fifth metatarsal fractures — both styloid avulsions (from peroneus brevis) and Jones fractures can involve the adjacent FDMB origin.
| Origin | Base of the fifth metatarsal and plantar surface of the long plantar ligament |
|---|---|
| Insertion | Lateral side of the base of the fifth toe proximal phalanx |
| Nerve Supply | Superficial branch of the lateral plantar nerve (S1, S2) |
| Blood Supply | Lateral plantar artery |
| Actions | Flexion of the fifth toe MTP joint; Assists in lateral plantar arch support |
|---|
By flexing the fifth toe MTP joint it contributes to the toe flexion needed to grip the ground during the push-off phase and maintains the little toe's contact with the ground during balance activities.
The FDMB of the foot is assessed alongside the other lateral plantar nerve muscles in tarsal tunnel syndrome evaluation. Like the ADM, its denervation produces lateral foot weakness and toe flexion impairment that is detectable by EMG but rarely prominent enough to be the presenting complaint.
Not individually palpable due to its deep position beneath the lateral plantar skin.
FDMB and adjacent muscle weakness from lateral plantar nerve compression contributing to lesser toe deformity and forefoot instability.
