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Sternocleidomastoid
functional anatomy

By Christy Cael

Originally published in Massage Bodywork magazine, July/August 2011. Copyright 2011. Associated Bodywork and Massage Professionals. All rights reserved.

The sternocleidomastoid (SCM) is a large, superficial muscle on the lateral neck. It has two heads and connects the mastoid process to the manubrium of the sternum and medial clavicle.

The muscle runs parallel to the ramus of the mandible and forms an upside-down "V" with the posteriorly oriented splenius capitis muscle. The SCM also divides two major sites of caution in the neck. It joins the trachea and inferior mandible to form the anterior triangle and the lateral edge of the upper trapezius and superior clavicle to form the posterior triangle. Accurate palpation of the SCM helps locate these vulnerable regions and avoids damaging the structures contained within.

Strong attachments to the temporal bone and an oblique position on the neck make the SCM a powerful prime mover for flexion, lateral flexion, and rotation. Because the muscle inserts posteriorly on the skull, it can extend the head and upper cervicals. Combined neck flexion and head extension creates a forward head motion, jutting the chin forward. Bilateral shortness in the SCM leads to a forward head posture or, if unilateral, a condition called torticollis (a laterally flexed and rotated neck).

Forward head posture is very common and easily identified. In normal posture viewed from the side, the opening of the ear should be aligned with the point of the shoulder (acromion process). The client's eyes should appear level or horizontally aligned with the external occipital protuberance near the base of the skull. Short SCMs pull the head forward, compared to the shoulder girdle, and tilt the head back. This makes the eyes appear higher than the base of the skull.

When positioned supine, the chin should align horizontally with the forehead from a side view. With forward head posture, the client's chin rests higher than the forehead and cervical lordosis is exaggerated. Lengthening the SCM helps reduce forward head posture, aligns the spine, and decompresses the vertebral joints.

Palpating The SCM
Positioning: client supine
1. Sit at the client's head and slightly rotate the head to the opposite side to slack tissue.

2. Locate the mastoid process with the thumb and slide anteriorly and caudally onto the thick SCM muscle.

3. Gently pincer-grasp the muscle belly and follow it toward the sternum and medial clavicle.

4. Instruct the client to lift his head from the table to ensure proper location.

Christy Cael is a licensed massage therapist, certified athletic trainer, and certified strength and conditioning specialist. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Kinesiology and Palpation for Manual Therapists (Lippincott Williams Wilkins, 2009). Contact her at functionalbook@hotmail.com.




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