Dorsal Interossei (Foot): Anatomy, Action, DAB Mnemonic & Testing

The Dorsal Interossei of the foot are four bipennate muscles located in the spaces between the metatarsal bones. While small, they are crucial for the stability of the toes during the push-off phase of walking. They are famous in anatomy for the mnemonic "DAB".

[Image of Dorsal Interossei Foot anatomy]

Quick Anatomy Snapshot

Count	Four muscles (1st, 2nd, 3rd, 4th).
Origin (Proximal)	Each muscle arises from the adjacent sides of two Metatarsal bones.
Insertion (Distal)	Bases of proximal phalanges and dorsal extensor expansions of toes 2, 3, and 4.
Nerve Supply	Lateral Plantar Nerve (S2, S3) - deep branch.
Blood Supply	Dorsal Metatarsal Arteries.
Primary Actions	Abduction: Spreads toes 2, 3, and 4 away from the midline. MTP Flexion: Flexes the Metatarsophalangeal joints. IP Extension: Extends the Interphalangeal joints.

Deep Dive: The "DAB" Concept

To understand these muscles, you must understand the midline of the foot.

1. The Midline Difference

In the Hand, the midline is the 3rd finger (middle finger).
In the Foot, the midline is the 2nd Toe.

Therefore, "Abduction" in the foot means moving away from the 2nd toe.

2. The "DAB" Mnemonic

Dorsal interossei ABduct.
Plantar interossei ADduct (PAD).

3. Insertion Specifics

Because the 2nd toe is the midline, it needs Dorsal Interossei on both sides so it can abduct in either direction.
• 1st Dorsal Interosseous: Medial side of 2nd toe.
• 2nd Dorsal Interosseous: Lateral side of 2nd toe.
• 3rd Dorsal Interosseous: Lateral side of 3rd toe.
• 4th Dorsal Interosseous: Lateral side of 4th toe.

Physio Corner: Clinical Relevance

💪 Functional Fact: You rarely abduct your toes voluntarily in isolation. These muscles function primarily during the "Toe Off" phase of gait to stabilize the metatarsals and keep the toes straight and gripping the ground.

Palpation

These muscles are palpable on the top (dorsum) of the foot. Place your fingers in the web spaces between the metatarsal shafts. Ask the patient to spread their toes against resistance. You will feel the muscle bellies firm up between the bones.

⚠️ Clinical Pathology: Claw Toe Deformity
Weakness or paralysis of the interossei (intrinsic minus foot) disrupts the balance of the toes. The long extensors (EDL) hyperextend the MTP joint, and the long flexors (FDL) curl the IP joints, resulting in "Claw Toes." The interossei normally prevent this by flexing the MTP and extending the IP joints.

Manual Muscle Testing (MMT)

Testing the ability to spread the toes.

Testing Tip: Many people have poor motor control of their toes. Do not confuse inability to perform the action with paralysis; check for palpable contraction.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Resistance)	Position: Supine or sitting. Foot neutral. Action: Patient spreads (abducts) the toes. Resistance: Therapist uses a pincer grip to push the 2nd, 3rd, or 4th toes inward (adduction) toward the midline. Grade 3: Visible abduction. Grade 4/5: Holds against finger pressure.
Grade 0, 1 (Palpation)	Action: Palpate the dorsal web spaces between metatarsals. Cue: "Try to spread your toes apart." Grade 1: Contraction felt between bones. Grade 0: No activity.

Frequently Asked Questions

Does the big toe have a dorsal interosseous?

No. The big toe (Hallux) has its own specialized abductor: the Abductor Hallucis. It does not need an interosseous muscle for this.

Does the little toe have a dorsal interosseous?

No. The 5th toe also has its own abductor: the Abductor Digiti Minimi. Therefore, Dorsal Interossei only attach to toes 2, 3, and 4.

What is the nerve supply exception?

While the Lateral Plantar Nerve supplies all interossei, the 1st and 2nd Dorsal Interossei sometimes receive extra innervation from the Deep Peroneal Nerve on the dorsal side.

Test Your Knowledge: Dorsal Interossei Quiz

1. What is the mnemonic for the action of the Dorsal Interossei?

2. How many Dorsal Interossei are there in the foot?

3. The midline of the foot passes through which digit?

4. Which nerve supplies the Dorsal Interossei?

5. The 2nd toe has how many Dorsal Interossei attached to it?

6. Dorsal Interossei originate from:

7. Besides abduction, what do these muscles do at the MTP joint?

8. Which toe does NOT receive an insertion from the Dorsal Interossei?

9. Where are these muscles located relative to the Plantar Interossei?

10. Weakness of the Interossei leads to which deformity?

References

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer.
• Standring, S. (2016). Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier.
• Brukner, P., & Khan, K. (2017). Clinical Sports Medicine. 5th ed. McGraw-Hill Education.