The four dorsal interossei of the foot abduct the second, third, and fourth toes away from the reference midline of the second toe (unlike the hand where the midline is the third finger). As in the hand, their DAB mnemonic (Dorsal interossei ABduct) distinguishes them from the plantar interossei which adduct. Their MTP flexion and IP extension intrinsic plus action helps stabilise the lesser toes during the propulsive phase of gait.
| Origin | Adjacent sides of the metatarsal bones bilaterally, two heads for each of the four dorsal interossei |
|---|---|
| Insertion | Bases of the proximal phalanges and extensor expansions of toes 2, 3, and 4 |
| Nerve Supply | Lateral plantar nerve (S1, S2) |
| Blood Supply | Dorsal and plantar metatarsal arteries |
| Actions |
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The first dorsal interosseous on the medial side of the second toe is the largest and best developed, providing stabilisation of the second MTP joint against the strong ground reaction forces during push-off, which is critical given the disproportionate loading the second metatarsal sustains.
Interosseous wasting in the foot from peripheral neuropathy (diabetes, Charcot-Marie-Tooth) produces visible metatarsal guttering and loss of second toe stability, contributing to second MTP joint plantar plate failure and crossover deformity. The first dorsal interosseous is the most accessible to clinical assessment and can be tested by resisting second toe abduction.
The dorsal interossei are palpable in the dorsal metatarsal spaces during toe abduction, with the first dorsal interosseous in the first intermetatarsal space between the first and second metatarsals being the most accessible.
Progressive foot interosseous wasting from diabetic or hereditary neuropathy producing toe deformity and forefoot pain managed with footwear modification and intrinsic strengthening.
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