Origin of the Extensor Hallucis Longus Muscle
The extensor hallucis longus (EHL) muscle originates from the middle three-fifths (or middle two-fourths) of the anterior surface of the fibula, medial to the origin of the extensor digitorum longus, and from the adjacent anterior surface of the interosseous membrane. 1, 2, 3
Anatomical Details
The standard anatomical origin can be described as follows:
- Primary fibular origin: The muscle arises from approximately the middle three-fifths of the medial (anteromedial) surface of the fibula 1, 4, 3
- Secondary origin: The anterior surface of the interosseous membrane, located medial to the extensor digitorum longus origin 2, 3
- Anatomical position: The EHL lies lateral to the tibialis anterior muscle and medial to the extensor digitorum longus 1, 4
Anatomical Variations
While the question asks about the typical origin, clinically relevant variations exist:
- Double origin variant: Rare cases demonstrate origin from both the medial aspect of the fibula AND the lateral aspect of the tibia, which can have surgical implications 5
- Independent muscle bellies: Additional muscle bellies may separate from the main EHL muscle belly at variable distances (3-6 cm) from the primary origin, forming structures like the extensor hallucis capsularis 4
- Shared origins: The peroneus tertius may occasionally originate as a lateral division of the EHL muscle belly rather than from the extensor digitorum longus 1
Clinical Relevance
Understanding these anatomical variations is critical in several contexts:
- Surgical planning: Knowledge of origin variations is essential during foot and leg surgery, particularly when addressing fractures of the tibia and fibula 5
- Post-surgical complications: Atypical origins can contribute to unexpected functional alterations, such as involuntary toe extension during plantar flexion when fibrosis develops around fixation plates 5
- Imaging interpretation: The common extensor origin at the lateral elbow can be evaluated with ultrasound, though this refers to upper extremity anatomy rather than the EHL 6