The Splenius capitis muscle is located in the back or the neck. It originates on the ligamentum nuchae and the spinous processes of C7 to T6. It attaches to the occipital bone and the mastoid process of the temporal bone. This muscle functions bilaterally to produce neck extension, and unilaterally to produce rotation of the head to the same side. When trigger points develop in this muscle they will produce restriction in neck movement, as well as pain felt in the neck, but also strongly in the top of the head. Trigger points in this muscle are a common cause of headaches.
The Teres major muscle is located at the back of the armpit. It originates on the posterior aspect of the inferior angle of the scapula, and inserts and inserts on the medial lip of the intertubercular sulcus of the humerus. It’s main function is to assist adduction, internal rotation, and extension of the arm. This muscle only becomes active when there is resistance added to these movements. Trigger point pain from this muscle will cause pain to be felt deep into the posterior shoulder and down the back of the arm.
The Teres minor muscle is on of the rotator cuff muscles. It originates on the lateral border of the scapula, and inserts on the inferior facet of the greater tubercle of the humerus. This muscle assists with external rotation of the humerus as well as shoulder stability. This muscle is often damaged with a shoulder injury. Trigger points will refer into the posterior deltoid and down the back of the arm.
The Subclavius muscle is a small muscle on the underside of the clavicle. It originates on the first rib and it’s cartilage, and inserts on the inferior clavicle. It’s main function is to assist in protraction of the shoulder. This muscle is often shortened and tight from poor rounded shoulder posture. When trigger points form in this muscle they can refer pain into the anterior shoulder and down the radial part of the arm. Pain can also be referred into the thumb and first two fingers.