The scalene muscles attach to the transverse processes of C2-C7 and insert into the 1st and 2nd rib trapping the 1st and second thoracic vertebrae. They laterally flex the neck and assist in inhalation by elevating the upper ribs.
They are key in Thoracic Outlet Syndrome as they elevate the first rib and trap the cervical nerves between the anterior and middle scalene muscles.
They vary in their attachments and size a great deal of the time (about 40-71% of the reviewed studies).
The anterior scalene muscle originates on the front of the C3-C6 and inserts on the 1st rib just anterior to the cervical nerves. This arrangement traps C7 and T1. There are reports of it extending to attach to the second rib as well.
Dissection information on the scalenus minimus is highly variable. It is reported from 7-71% of the time and varies in its attachments.
This muscle, when present, usually attaches to the anterior tubercle of C7, and, at times, C6. It inserts on the fascia of the pleural cavity and, often, the tubercle of the first rib.
The middle scalene originates on the posterior tubercle of the transverse processes of C2 through C6 or C7 and inserts on the first rib posterior to the cervical plexus. This traps C7-T1 between origin and insertion.
The posterior scalene muscle originates on the posterior tubercles of the C5-C7 and inserts on the external aspect of the second rib trapping T1and T2 between the attachments.
Tony Preston has a practice in Atlanta, Georgia where he sees clients.
He has written and taught about anatomy, trigger points and cranial therapies since the mid-90s.