The scalenus posterior is the smallest of the scaleni muscles in the neck. It connects the lower two cervical vertebrae to the second rib. It is inserted onto the post/lateral surface of the rib. The scalenus posterior flexes the cervical vertebrae when it acts unilaterally. It also flexes the neck and raises the second rib when it acts bilaterally. Its synergists include the longus capitus, logus coli, scalenus medius, and the scalenus interior. Its nerve supply includes the posterior branches C5, C6, C7, and C8. Injury to the scalenus posterior may result in scalenus anticus syndrome. This results in pain to the chest, shoulders, back, and arms. In extreme cases, the scalenus posterior may decrease blood flow to the hands, making them numb and cold. Scalenus anticus syndrome may be treated through myofascial release and neck adjustment by a chiropractor. Such treatment would relieve pressure on the nerves and blood vessels by relieving the tension in the muscles and reducing the abnormal motion of the neck.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Scalenus posterior