Adductor Hallucis: Origin, Insertion, Nerve, Action & Bunions

The Adductor Hallucis is a deep intrinsic muscle of the foot shaped like the number "7." Unlike the abductor which is superficial, this muscle lies deep within the sole. It is composed of two distinct heads (Oblique and Transverse) and acts as the primary antagonist to the Abductor Hallucis.

[Image of Adductor Hallucis muscle anatomy]

Quick Anatomy Snapshot

Origin (Proximal)	1. Oblique Head: Bases of Metatarsals 2-4 and the sheath of Peroneus Longus. 2. Transverse Head: Plantar metatarsophalangeal ligaments of toes 3-5.
Insertion (Distal)	Lateral side of the base of the Proximal Phalanx of the 1st digit (Big Toe).
Nerve Supply	Lateral Plantar Nerve (Deep Branch) - S2, S3.
Blood Supply	Plantar Metatarsal Arteries.
Primary Actions	Adduction: Pulls the big toe towards the 2nd toe. Arch Support: The Transverse head maintains the Transverse Arch of the foot. Flexion: Assists in flexing the 1st MTP joint.

Deep Dive: The "Number 7" Muscle

The Adductor Hallucis is unique because its two heads are separated by a gap through which plantar vessels pass.

1. The Oblique vs. Transverse Head

The Oblique Head is large and fleshy, running diagonally across the foot. The Transverse Head is a small, narrow strip running horizontally across the ball of the foot. Together, they pull the big toe inward.

2. Midline of the Foot

In the hand, the midline is the 3rd finger. In the foot, the midline is the 2nd toe. Therefore, "Adduction" of the big toe means pulling it towards the 2nd toe (lateral movement), not towards the other foot.

Physio Corner: Clinical Relevance

💪 Functional Fact: The Transverse Head acts like a "tie-beam" for the Transverse Arch. When you stand on your toes (tiptoes), this muscle contracts to prevent the metatarsal heads from splaying apart.

Palpation

This muscle is very difficult to palpate directly as it lies deep to the flexor tendons and the lumbricals. Deep pressure in the center of the plantar aspect of the foot (between the 1st and 2nd metatarsals) may reveal tenderness in the Oblique head.

⚠️ Clinical Pathology: Bunions (Hallux Valgus)
The Adductor Hallucis is the "villain" in bunion formation. When it becomes tight, it pulls the big toe laterally (towards the 2nd toe). Because its insertion is on the phalanx, this pull causes the metatarsal head to push medially, creating the bony bump. Releasing this muscle is a key step in bunion surgery.

Manual Muscle Testing (MMT)

Testing adduction of the big toe is rarely done in isolation but is useful for assessing intrinsic foot control.

Testing Tip: Most people cannot voluntarily adduct their big toe without flexing it.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Resistance)	Position: Supine or sitting with foot relaxed. Action: Patient attempts to pull the big toe towards the 2nd toe. Resistance: Applied at the medial side of the proximal phalanx, pulling the toe medially (away from the 2nd toe). Grade 3: Range of motion achieved. Grade 4/5: Holds against resistance.
Grade 0, 1 (Palpation)	Action: Palpate deep in the web space between the 1st and 2nd metatarsals. Cue: "Try to squeeze your big toe against your second toe."

Frequently Asked Questions

Why is it supplied by the Lateral Plantar Nerve?

Even though it moves the big toe (medial side), the muscle belly lies deep in the central/lateral aspect of the foot, falling into the territory of the Lateral Plantar Nerve (similar to the Ulnar nerve supplying the Adductor Pollicis in the hand).

Does it cause the arch to collapse?

No, it actually helps support the Transverse Arch. However, if it is tight and the Abductor Hallucis is weak, the resulting bunion deformity can destabilize the medial longitudinal arch.

How do I stretch the Adductor Hallucis?

By using a toe spacer (specifically between the 1st and 2nd toe) or manually pulling the big toe away from the 2nd toe (medial abduction) while massaging the sole of the foot.

Test Your Knowledge: Adductor Hallucis Quiz

1. Which nerve supplies the Adductor Hallucis?

2. The Adductor Hallucis has two heads: Oblique and ________?

3. What is the primary role of the Transverse Head?

4. Where does the Adductor Hallucis insert?

5. Tightness in this muscle contributes to which deformity?

6. In the foot, "Adduction" of the big toe moves it towards:

7. The Adductor Hallucis is located in which plantar layer?

8. The shape of the Adductor Hallucis resembles which number?

9. Which tendon sheath does the Oblique Head originate from?

10. To bias the Adductor Hallucis during MMT, resistance is applied:

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.