The trapezius muscle originates from the inion to T12 and inserts into the clavicle, acromion and spine of the scapula. It is most prominent as it runs from the side of the neck towards the acromion.


The trapezius muscle is often stretched in flexion injuries causing tenderness to palpation. Tenderness is most often found in the superior lateral portion of the muscle.

The trapezius and sternocleidomastoid are both innervated by the spinal accessory nerve (cranial nerve IX). This is a result of the fact that these two muscles originate as one embryologically. The also share a common origin at the mastoid process.