The ligamentum nuchae is a large median ligament composed of tendons and fascia located between the posterior muscles of the neck. It covers the spines of C1 to C6 vertebrae. It is a superior and posterior extension of the supraspinous ligament. It rises from the spinous process of C7 to the inion of the occipital bone, attaching all the posterior tips of the spinous processes in between. It is thick and strong, limiting hyperflexion of the neck.
In quadriped animals, it is very strong and functions in keeping the neck and head of the animal up.
The ligamentum nuchae consists of the dorsal raphe and medial septal parts. The dorsal raphe attaches to muscles while the medial septum does not.
The dorsal raphe is superficial to the posterior midline of the neck. It extends from the occipital protuberance to the spinous process of the C7 vertebra. The superior portion consists of medial fibers from the cervical trapezius. The inferior portion consists of interweaving tendons from splenius capitis and rhomboid minor.
The medial septum extends from the ventral surface of the dorsal raphe. The medial septum isolates the semispinalis capitis ventrally and laterally. Thus, the semispinalis cervicis, multifidus and opposite semispinalis capitis remain separate.
The medial septum runs deep into the vertebral column. It reaches depths as far as the ligamentum flavum. The medial septum blends into the posterior atlanto-occipital membrane and the posterior atlanto-axial membrane (upper portion of the ligamentum flavum between C1 and C2). It is attached to the posterior spinal dura along these membranes.