Inferior rectus muscle

Last revised by Craig Hacking ◉ on 27 Dec 2021

Citation, DOI, disclosures and article data

Citation:

Jones J, Hacking C, Worsley C, et al. Inferior rectus muscle. Reference article, Radiopaedia.org (Accessed on 27 Mar 2025) https://doi.org/10.53347/rID-10418

DOI:

https://doi.org/10.53347/rID-10418

Permalink:

https://radiopaedia.org/articles/10418?embed_domain=staging.radpair.com

rID:

10418

Article created:

12 Aug 2010, Jeremy Jones ◉

Disclosures:

At the time the article was created Jeremy Jones had no recorded disclosures.

View Jeremy Jones's current disclosures

Last revised:

27 Dec 2021, Craig Hacking ◉

Disclosures:

At the time the article was last revised Craig Hacking had no recorded disclosures.

View Craig Hacking's current disclosures

Revisions:

15 times, by 10 contributors - see full revision history and disclosures

Systems:

Head & Neck

Sections:

Anatomy

Tags:

refs, cases

Synonyms:

Inferior rectus

The inferior rectus muscle is one of the six extraocular muscles that control eye movements.

innervation: inferior branch of the oculomotor nerve (CN III)
origin: annulus of Zinn (tendinous ring)
insertion: globe (anterior, inferior surface)
primary function: one of two ocular depressors
secondary function: one of the two ocular external rotators
tertiary function: one of the three ocular adductors

Gross anatomy

Origin

Inferior rectus, along with the other rectus muscles, arises from the annulus of Zinn, the common tendinous ring at the apex of the orbit that surrounds the optic canal ¹.

Insertion

Inferior rectus runs anteriorly on the inferior surface of the eye and inserts into the inferior surface of the sclera just posterior to the junction of cornea and sclera ².

Relations

Inferior rectus is crossed by the inferior oblique muscle, which runs inferior to it as it crosses the floor of the orbit.

Arterial supply

Branches of the ophthalmic artery, itself a branch of the internal carotid artery.

Innervation

Innervated by the oculomotor nerve, which also supplies medial rectus, superior rectus, and inferior oblique muscles.

Action

The primary action of the inferior rectus is to depress the eye (see figure 1) ¹. However, because the apex of the orbit is placed medially in the skull, the orbital axis that the inferior rectus runs in does not correspond with the optical axis of the eye in its neutral position. This means that the inferior rectus has secondary actions of adduction and external rotation (see figures 2 and 3).

If the eye is abducted by the lateral rectus such that the optical axis lines up with the orbital axis, the inferior rectus produces ocular depression only, and is solely responsible for this movement. Thus, when the physician testing eye movements first asks the patient to follow their finger laterally then inferiorly in the familiar H-shape, the inferior rectus muscle (and the oculomotor nerve that supplies it) are being directly tested.

If the eye is adducted by the medial rectus, the orbital axis runs almost perpendicular to the optical axis, so the inferior rectus no longer produces effective ocular depression, and instead produces external rotation and adduction.