Inferior Oblique
Extraocular · Head & Neck
The inferior oblique is the only extraocular muscle that arises from the front of the orbit rather than its apex. It originates from the orbital surface of the maxilla, lateral to the lacrimal groove, and passes backward and laterally beneath the eyeball to insert on the posterolateral sclera behind the equator, deep to the lateral rectus. Its posterolateral line of pull produces extorsion (lateral rotation), elevation, and abduction, and it elevates the eye most effectively when the eye is adducted. It is supplied by the inferior division of the oculomotor nerve (CN III).
Origin, Insertion, Action & Nerve
Origin
Orbital surface of the maxilla, lateral to the lacrimal groove
Insertion
Posterolateral sclera posterior to the equator, deep to the lateral rectus
Action
Extorts (laterally rotates), elevates, and abducts the eyeball; elevates the adducted eye
Nerve
Inferior division of the oculomotor nerve (CN III)
Attachments explained
The Inferior Oblique is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Orbital surface of the maxilla, lateral to the lacrimal groove
Insertion
Posterolateral sclera posterior to the equator, deep to the lateral rectus
Action & function
When the Inferior Oblique contracts, it produces the following movements: Extorts (laterally rotates), elevates, and abducts the eyeball; elevates the adducted eye.
As part of the Extraocular group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Inferior Oblique receives its nerve supply from the Inferior division of the oculomotor nerve (CN III).
Because a muscle can only contract when its nerve is intact, injury to the Inferior division of the oculomotor nerve can weaken or paralyse the Inferior Oblique, impairing the movements it normally produces (extorts (laterally rotates), elevates, and abducts the eyeball). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Inferior Oblique (the OIANS method)
Study the inferior oblique as the mirror image of the superior oblique: both attach behind the equator and both abduct and rotate the eye, but the inferior oblique extorts and elevates whereas the superior oblique intorts and depresses. Because it approaches the globe from the front and below, its elevating action is best seen when the eye is adducted, which is precisely how it is isolated on examination.
Fix its nerve by placing it with the other muscles of the inferior division of the oculomotor nerve, the inferior and medial recti. It is the sole extraocular muscle to originate at the anterior orbit, a distinctive feature worth remembering, and it forms a functional pair with the superior rectus, since both elevate the eye in different positions of gaze.
Frequently asked questions
Where is the Inferior Oblique located?
The Inferior Oblique is a muscle of the Extraocular group, located in the Head & Neck.
What is the origin of the Inferior Oblique?
Orbital surface of the maxilla, lateral to the lacrimal groove
What is the insertion of the Inferior Oblique?
Posterolateral sclera posterior to the equator, deep to the lateral rectus
What movements does the Inferior Oblique produce?
Extorts (laterally rotates), elevates, and abducts the eyeball; elevates the adducted eye
What nerve supplies the Inferior Oblique?
Inferior division of the oculomotor nerve (CN III)
Is the Inferior Oblique free to study in OIANS?
The Inferior Oblique is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Head & Neck is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Inferior Oblique
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