Middle Scalene

Origin, Insertion, Action, Innervation

Origin: Posterior tubercles of the transverse processes of C2–C7
Insertion: Superior surface of the first rib, posterior to the subclavian groove (behind the groove for the subclavian artery)
Action:
Primary: Lateral flexion of the cervical spine (ipsilateral)
Elevation of the first rib (accessory muscle of respiration)
Flexion of the cervical spine (bilateral contraction, minor)
Innervation: Ventral rami of C3–C8

Palpation Guide

Client position: Supine with head in neutral.
Landmark sequence:

Locate the anterior scalene (deep to the clavicular head of SCM). The middle scalene lies immediately posterior to the anterior scalene.
Place your fingertip just posterior to where you located the anterior scalene, in the groove between the anterior scalene and the posterior cervical musculature. The middle scalene occupies this space.
Palpate superiorly toward the transverse processes — the middle scalene arises from C2–C7, extending higher than the anterior scalene (C3–C6).
Trace inferiorly toward the first rib — the middle scalene inserts posterior to the subclavian groove, behind the insertion of the anterior scalene.

Tissue feel: Slightly larger and more substantial than the anterior scalene. It feels like a firm, elongated cord running from the lateral cervical spine to the first rib. Because it is the largest scalene, it is often the easiest to palpate.
Confirmation test: Ask the client to laterally flex the neck ipsilaterally against gentle resistance. The middle scalene contracts between your palpating fingers. Deep inspiration will also engage it.
Common errors:
Confusing middle scalene with posterior scalene — posterior scalene is smaller, lies behind middle scalene, and inserts on the second rib instead of the first.
Not distinguishing middle from anterior scalene — the brachial plexus emerges between these two muscles. The anterior scalene is more medial and anterior; the middle scalene is more lateral and posterior.
Working too aggressively in the interscalene interval — the brachial plexus and subclavian artery are in the space between the anterior and middle scalenes.

Trigger Point Referral

Common TrP locations: A primary TrP in the mid-belly at approximately C4–C5 level. A secondary TrP closer to the first rib attachment.
Referral pattern: Refers to the anterior and posterior chest (pectoral and interscapular regions), down the lateral arm to the radial forearm, and into the hand — particularly the index and middle fingers. Also refers to the medial scapular border.
Clinical significance: The referral down the arm to the hand overlaps with C6–C7 radiculopathy and median nerve entrapment. If neurological testing is normal (intact reflexes, no dermatomal sensory loss, no myotomal weakness), the symptoms may be scalene TrP referral rather than nerve pathology.

Trigger point referral diagram — coming soon

Image coming soon. For visual reference, see [Scalenes at TriggerPoints.net](http://www.triggerpoints.net/muscle/scalene).

Clinical Notes

Innervation significance:

Receives innervation from C3–C8 ventral rami — the broadest segmental innervation of the three scalenes. This wide range means that cervical disc or foraminal pathology at almost any level can produce reflex scalene spasm.

Common conditions:

Along with the anterior scalene, the middle scalene is directly involved in conditions/thoracic-outlet-syndrome. It forms the posterior wall of the interscalene triangle, and hypertrophy or hypertonicity narrows the triangle from behind.
Contributing muscle in conditions/cervical-radiculopathy mimicry — TrP referral to the arm and hand can closely match dermatomal patterns.
Bilateral hypertonicity contributes to first-rib elevation, which is a component of conditions/thoracic-outlet-syndrome via the costoclavicular mechanism.

What you'll typically find:

The middle scalene is almost always involved when the anterior scalene is hypertonic — the three scalenes function as a unit and rarely develop isolated dysfunction. When palpating one scalene, always assess all three.
In chest-breathers, the middle scalene is hypertonic bilaterally and contributes to the elevated first-rib position. Palpation of the first rib attachment reveals tenderness.
Because it is the largest scalene, it is often the most palpable and the one students find first when learning scalene palpation.

Treatment effects:

Same treatment principles as anterior scalene — use short-duration sustained compression (20–30 seconds) and monitor for arm paresthesia. The brachial plexus is immediately anterior to the middle scalene.
Pin-and-stretch technique is effective — compress the TrP while passively laterally flexing the neck to the contralateral side.
Rib mobilization (first rib depression) can be a useful adjunct — if the first rib is elevated, manual depression during exhalation can relieve scalene tension.

Cautions:

The brachial plexus emerges between the anterior and middle scalenes — pressure on the middle scalene can push the plexus against the anterior scalene. Monitor for arm paresthesia.
The long thoracic nerve (C5–C7) often pierces the middle scalene or passes behind it. Compression can contribute to serratus anterior weakness and scapular winging.
The dorsal scapular nerve (C5) may pierce the middle scalene. Entrapment here can produce medial scapular border pain and rhomboid weakness.

Postural significance:

Functions with the anterior and posterior scalenes as a lateral cervical stabilizer. Chronic bilateral hypertonicity elevates both first ribs and maintains the chest-breathing pattern. In upper crossed syndrome, the scalene group contributes to the forward-head posture by fixing the cervical spine in a laterally stiffened position.

Clinical pearl:

The long thoracic nerve often passes through or directly behind the middle scalene. If a client presents with serratus anterior weakness (scapular winging) and cervical symptoms, investigate middle scalene hypertonicity as a potential compression site for the long thoracic nerve. This is an underrecognized cause of scapular winging.

Assessment

Manual muscle testing:

Cervical lateral flexion: Client supine. Ask the client to laterally flex the neck ipsilaterally against resistance. This tests all three scalenes together — they cannot be isolated by manual muscle testing.

Stretch test:

Cervical contralateral lateral flexion with slight extension: Client supine. Laterally flex the neck to the contralateral side with slight extension and ipsilateral rotation. This stretches the middle scalene specifically. Compare bilaterally.

Related special orthopedic tests:

Adson's test — anterior scalene compression of subclavian artery
Roos test (EAST) — neurogenic thoracic outlet syndrome
Cervical compression test — to rule out cervical radiculopathy

Muscle Groups

Scalene group (anatomical):

Cervical lateral flexors (functional):

Accessory respiratory muscles (functional):

Related Muscles

Synergists for cervical lateral flexion:

anatomy/muscles/anterior-scalene — forms the anterior wall of the interscalene triangle
anatomy/muscles/posterior-scalene — smallest scalene; attaches to the second rib

Antagonists:

Contralateral scalenes — opposing lateral flexion

Clinically related:

anatomy/muscles/serratus-anterior — the long thoracic nerve that innervates it often passes through or behind the middle scalene

Key Takeaways

Largest scalene — the most palpable and often the first scalene students identify.
The long thoracic nerve passes through or behind it — middle scalene hypertonicity is an underrecognized cause of serratus anterior weakness and scapular winging.
Always assess all three scalenes as a unit — isolated dysfunction is rare.