The trapezius is a major muscle of the back in the most superficial layer that extends from the occipital bone down to the lower thoracic vertebrae and laterally to the scapula. This muscle moves and stabilizes the scapula.

• Origin: spinous processes of the seventh cervical and the following twelve thoracic vertebrae (C7 - T12), from the nuchal ligament, occipital protuberance and the superior nuchal line.
• Insertion: lateral third of the clavicle, the acromion and spine of the scapula.
• Action: rotates, raises, lowers, and adducts the scapula. It also aids in rotating the head.
• Innervation: motor innervation of the trapezius is provided by the accessory nerve (CN XI); motor innervation and proprioception - by the third and fourth cervical spinal nerves (C3 - C4) that arise from the cervical plexus.