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F r e e S O A P n o t e s w i t h M a s s a g e B o o k f o r A B M P m e m b e r s : a b m p . u s / M a s s a g e b o o k 49 FUNCTIONAL ANATOMY education Subclavius By Christy Cael The subclavius is a small muscle located in the anterior shoulder girdle. It resides high on the chest between the clavicle and 1st rib and deep to the clavicular portion of the pectoralis major. The subclavius originates medially near the manubrium of the sternum on the costocartilage junction of the 1st rib. The muscle fibers run superiorly and laterally between the 1st rib and clavicle, then insert along a groove on the underside of the middle third of the clavicle. The subclavius muscle is in close proximity to the brachial plexus and subclavian vessels that run from the cervical region, between the 1st rib and clavicle, and into the upper extremity. The subclavius functions mainly to stabilize or fix the clavicle during movements of the arm and/ or shoulder girdle. When activated, it pulls the clavicle downward, closing the space between it and the 1st rib. The subclavius muscle works on the sternoclavicular and acromioclavicular joints, both of which have strong ligaments and therefore limited mobility. Most of the movement provided by the subclavius occurs at the sternoclavicular joint and accompanies movement at the glenohumeral joint. Similar in function to the scalene muscles, the subclavius may assist with inhalation by elevating the 1st rib. Forceful inhalation or dysfunctional breathing may lead to hypertonicity and associated pain or dysfunction in the subclavius as well as synergistic muscles like the pectoralis major and minor, scalenes, and external intercostals. Other activities that may result in over-activation or shortening of the subclavius include repetitive lifting or prolonged positioning of the arm in front of SUBCLAVIUS Attachments • Origin: 1st rib at the junction with the costocartilage • Insertion: Middle ¹⁄ ³ of inferior surface of the clavicle Actions • Fixes the clavicle inferiorly and anteriorly • Elevates the 1st rib • Helps depress the scapula, drawing the shoulder inferiorly and anteriorly Innervation • A nerve from the brachial plexus • C5–6 Subclavius