Obliquus capitis inferior muscle

The obliquus capitis inferior muscle is a muscle in the upper back of the neck. It is one of the suboccipital muscles. Its inferior attachment is at the spinous process of the axis; its superior attachment is at the transverse process of the atlas. It is innervated by the suboccipital nerve. The muscle rotates the head to its side.
Despite what its name suggest, it is the only capitis muscle that does not actually attach to the skull.

Anatomy

The obliquus capitis inferior is one of the suboccipital muscles. It is larger than the obliquus capitis superior muscle. It forms the inferolateral boundary of the suboccipital triangle.
The muscle extends laterally and somewhat superiorly from its inferior attachment to its superior attachment.

Attachments

its inferior attachment is at the lateral external aspect of the bifid spinous process of the axis (cervical vertebra C2) and the lamina of the axis.
Its superior attachment is at the transverse process of the atlas (cervical vertebra C1).

Innervation

The muscle receives motor innervation from the suboccipital nerve.

Relations

It lies deep to the semispinalis capitis and trapezius muscles.

Actions/movements

The muscle acts to rotate the atlas ipsilaterally. It acts together with the rectus capitis posterior major muscle.

Function

The muscle is responsible for rotation of the head and first cervical vertebra.
The obliquus capitis inferior muscle, like the other suboccipital muscles, has an important role in proprioception. This muscle has a very high density of Golgi organs and muscle spindles which accounts for this. It is believed that proprioception may be the primary role of the inferior oblique, allowing accurate positioning of the head on the neck.