The obliquus capitis inferior is a fleshy, thick muscle located in the neck. It is the bigger and longer of the two oblique muscles in the neck.
This muscle originates from the outer part of the spinous process of the second cervical vertebra, also called the axis. (The spinous process is a part of the bone that sticks out of the back, central portion of the vertebra.) The muscle travels slightly upward and laterally (sideways), and inserts into the posterior (back) and lower portion of the wing of the atlas, which is the topmost cervical vertebra. It makes up the inferior (bottom) border of a region in the neck called the sub-occipital triangle.
The muscle performs the key role of providing rotation of the atlas on the axis. It is named similarly to other capitis muscles, but it is the only muscle that does not connect with the cranium, the part of the skull that houses the brain.
The obliquus capitis inferior performs a significant function in proprioception, which is similar to the function of other sub-occipital muscles. Proprioception is the sense we have of our body’s position and movement. A dense presence of Golgi tendon organs enable it to perform this role. Golgi tendon organs are a type of nerve tissue that relays information about the flexing and releasing of muscles. This may be the main function of this muscle along with other sub-occipital muscles, because it facilitates the precise positioning of the head over the neck.