The superior oblique muscle is the longest extraocular muscle with the longest tendon. It is also connected to the superior rectus muscle by a frenulum of the intermuscular septum.

After the superior oblique arises, it travels along the medial aspect of the roof of the orbit to reach the trochlea. The trochlea is a fibrocartilaginous pulley-like structure found at the trochlear fovea of the frontal bone inside the superomedial orbital rim.

The superior oblique muscle passes through the trochlea, changes its direction and turns posterolaterally to cross the eyeball. Further, it travels inferior to the superior rectus muscle to reach its insertion site.

Origin: periosteum of the body of the sphenoid bone adjacent to the annulus of Zinn.

Insertion: trochlea at the orbital rim, posterior and superior surfaces of the sclera slightly posterior to the insertion site of the superior rectus muscle.

Action: depression, abduction, and intorsion (medial rotation) of the eyeball.

Innervation: trochlear nerve (CN IV).

Blood supply: superior muscular branch of the ophthalmic artery.

Venous drainage: superior and inferior orbital veins that further drain into the cavernous sinus.

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Superior oblique muscle