Posterior Scalene Muscle, Lateral View

Description

Running obliquely along the lateral cervical spine, the posterior scalene lies deep to the sternocleidomastoid and posterolateral to the middle scalene, its fibers descending inferolaterally toward an insertion on the second rib. Superiorly, the muscle takes origin from the posterior tubercles of the transverse processes of C4 to C6, sitting anterior to the levator scapulae and blending with the prevertebral fascia that invests the scalene group. Superficial context includes the platysma and sternocleidomastoid, while posteriorly the trapezius edge and deltoid cap frame the shoulder; craniofacial muscles such as the masseter and orbicularis oculi remain visible as regional landmarks. Deep and tight. Functionally, the posterior scalene elevates the second rib during inspiration and contributes to lateral flexion of the cervical spine, but its teaching value often centers on the scalene interval and thoracic outlet anatomy. The muscle forms the posterior boundary of the interscalene space, where the roots and trunks of the brachial plexus and the subclavian artery course between the anterior and middle scalenes, and where cervical ribs or scalene hypertrophy can contribute to neurogenic thoracic outlet syndrome with paresthesia in the ulnar distribution. For procedural anatomy, this lateral dissection-style view helps you explain why interscalene brachial plexus blocks target the groove between the anterior and middle scalenes rather than the posterior scalene, and why posterior scalene trigger points can refer pain into the shoulder girdle. Use this illustration in gross anatomy and regional head-and-neck modules to orient learners to layered cervical musculature, and in anesthesia or pain-medicine materials to support discussions of scalene-related entrapment and injection planning. It also fits surgical anatomy content covering supraclavicular exposure and rib mechanics in accessory respiratory muscle recruitment. Anatomical accuracy verified by SciePro's Medical Advisory Board.