Extensor Hallucis Longus: Origin, Insertion, Nerve, Action & Big Toe Function

The Extensor Hallucis Longus (EHL) is a thin muscle situated deep in the anterior compartment of the leg, sandwiched between the Tibialis Anterior and the Extensor Digitorum Longus. It is the primary extensor of the big toe (Hallux) and a vital muscle for clearing the foot during the swing phase of gait.

[Image of Extensor Hallucis Longus muscle anatomy]

Quick Anatomy Snapshot

Origin (Proximal)	Middle half of the anterior surface of the Fibula and the Interosseous Membrane.
Insertion (Distal)	Dorsal surface of the base of the Distal Phalanx of the Big Toe (Hallux).
Nerve Supply	Deep Peroneal (Fibular) Nerve (L5, S1).
Blood Supply	Anterior Tibial Artery.
Primary Actions	Big Toe Extension: Extends the MTP and IP joints of the 1st digit. Dorsiflexion: Assists in lifting the foot at the ankle. Inversion: Weak assistance (varies by foot position).

Deep Dive: The "Hidden" Muscle

In the upper leg, the EHL is hidden beneath the Tibialis Anterior and Extensor Digitorum Longus. It only becomes superficial in the distal third of the leg.

1. The Neurovascular Guide

The EHL serves as a landmark for the Anterior Tibial Artery and the Deep Peroneal Nerve. These vital neurovascular structures run deep to the muscle belly in the upper leg but emerge to lie between the EHL and EDL tendons at the ankle. Checking the "Dorsalis Pedis" pulse involves palpating just lateral to the EHL tendon.

2. Mechanical Advantage

Because it inserts on the distal phalanx, the EHL has a long lever arm. This makes it very effective at lifting the tip of the big toe, which is crucial to prevent tripping (stubbing the toe) while walking.

Physio Corner: Clinical Relevance

💪 Functional Fact: "Turf Toe" (hyperextension injury) usually involves damage to the plantar structures, but rehabilitation must involve strengthening the EHL to restore balance and range of motion to the MTP joint.

Palpation

Ask the patient to lift their big toe straight up against resistance. The EHL tendon will stand out prominently on the dorsum of the foot and ankle. It is the thick tendon running directly to the big toe, lateral to the Tibialis Anterior tendon.

⚠️ Clinical Pathology: L5 Radiculopathy
The EHL is the specific "key muscle" for testing the L5 spinal nerve root. Weakness in big toe extension (without other deficits) is a strong indicator of an L5 disc herniation or nerve root compression.

Manual Muscle Testing (MMT)

We test the extension of the big toe, specifically focusing on the interphalangeal (IP) joint.

Testing Tip: Isolate the Big Toe. Do not let the patient substitute by just dorsiflexing the ankle (using Tibialis Anterior).

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Resistance)	Position: Sitting or Supine. Ankle in neutral. Action: Patient extends the big toe (lifts it toward the shin). Resistance: Applied to the dorsal aspect of the Distal Phalanx of the big toe, pushing down into flexion. Grade 3: Full range against gravity. Grade 4/5: Holds against moderate/max resistance.
Grade 2 (Gravity Eliminated)	Position: Side-lying (rarely used) or Supine with heel supported. Action: Patient attempts to extend the big toe. Result: Full range of motion.
Grade 0, 1 (Palpation)	Action: Palpate the tendon on the dorsum of the 1st metatarsal. Cue: "Try to lift your big toe." Grade 1: Tendon tension felt. Grade 0: No activity.

Frequently Asked Questions

Does EHL assist in inversion?

Yes, weakly. Because it passes medial to the axis of the subtalar joint, it can assist the Tibialis Anterior in inverting the foot during dorsiflexion.

What causes "Claw Hallux"?

If the intrinsic muscles of the foot are weak, the EHL pulls the MTP joint into extension while the FHL pulls the IP joint into flexion, creating a clawed deformity of the big toe.

Is EHL the only extensor of the big toe?

No. The Extensor Hallucis Brevis (part of EDB) also extends the big toe, but it only acts on the proximal phalanx (MTP joint), not the tip (IP joint).

Test Your Knowledge: EHL Quiz

1. Weakness of the EHL is a hallmark sign of which nerve root pathology?

2. Where does the EHL insert?

3. Which nerve supplies the EHL?

4. The EHL muscle belly originates from the:

5. To locate the Dorsalis Pedis pulse, you should palpate lateral to the:

6. Besides toe extension, what action does EHL perform?

7. The EHL passes under which retinaculum?

8. Which muscle lies lateral to the EHL in the lower leg?

9. To test MMT Grade 5, where is resistance applied?

10. True or False: EHL is the only muscle that extends the big toe.

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.
• Magee, D. J. (2014). Orthopedic Physical Assessment. 6th ed. Elsevier.