The inferior rectus muscle is a muscle in the orbit near the eye. It is one of the four recti muscles in the group of extraocular muscles. It originates from the common tendinous ring, and inserts into the anteroinferior surface of the eye. It depresses the eye (downwards).
Structure
The inferior rectus muscle originates from the common tendinous ring (annulus of Zinn). It inserts into the anteroinferior surface of the eye. This insertion has a width of around 10.5 mm.
Relations
The insertion of the inferior rectus muscle is around 6 mm from the insertion of the medial rectus muscle, and around 8 mm from the insertion of the lateral rectus muscle. This may cause inferior rectus palsy, where the eye cannot be depressed.
Clinical significance
Strabismus
If the inferior rectus muscle is damaged, weak, or paralysed, this can cause strabismus. This can lead to elevation of the eye, as the superior rectus muscle remains stronger.
Surgery
Any surgery on the inferior rectus muscle may damage the parasympathetic branches to the ciliary muscles of the pupil.