The third dorsal interosseous occupies the third intermetatarsal space and abducts the third toe laterally. Along with the fourth dorsal interosseous, it contributes to maintaining the transverse spread of the forefoot during gait. Its functional importance is less than the first dorsal interosseous but becomes clinically relevant in intrinsic minus foot deformities.
| Origin | Adjacent surfaces of the third and fourth metatarsals (bipennate) |
|---|---|
| Insertion | Lateral base of the proximal phalanx of the third toe and extensor hood |
| Nerve Supply | Lateral plantar nerve (deep branch) |
| Blood Supply | Third plantar metatarsal artery |
| Actions | Abducts the third toe toward the fourth toe; Assists MTP flexion of the third toe |
|---|
The third dorsal interosseous is rarely assessed in clinical practice but is included in comprehensive EMG studies of the foot intrinsics for peripheral neuropathy staging. Third intermetatarsal space Morton's neuroma affects the common digital nerve running adjacent to this muscle. Wasting of the third intermetatarsal space contributes to broadening of the forefoot in intrinsic minus deformity.
Palpated in the third intermetatarsal space on the dorsum of the foot. Less prominent than the first dorsal interosseous due to smaller belly size.
Common digital nerve entrapment in the third intermetatarsal space adjacent to the third dorsal interosseous, producing burning metatarsalgia and numbness between the third and fourth toes, confirmed by Mulder's click test.
