Anterior Scalene

Clinical Notes

• Innervated by C5–C7 ventral rami — the same nerve roots that form the upper and middle trunks of the brachial plexus. Hypertonicity of the anterior scalene can compress the very nerve roots that innervate it, creating a self-perpetuating cycle of compression and spasm.

• Primary muscle in conditions/thoracic-outlet-syndrome (neurogenic and vascular). The brachial plexus and subclavian artery pass between the anterior and middle scalenes in the interscalene triangle. Hypertonic scalenes narrow this triangle and compress the neurovascular bundle.
• Scalene TrPs produce a pain pattern that overlaps significantly with conditions/cervical-radiculopathy at C5–C6. The referral to the chest, deltoid, and thumb/index finger distribution is nearly identical.
• Accessory respiratory muscle — chronic hypertonicity develops in clients with conditions/asthma, chronic obstructive pulmonary disease, or anxiety-related hyperventilation patterns. Chest-breathers chronically overwork the scalenes.
• Contributes to first-rib elevation in conditions/thoracic-outlet-syndrome — an elevated first rib narrows the costoclavicular space.

• In clients who are chest-breathers (respiratory pattern dysfunction), the scalenes are bilaterally hypertonic and tender. Watch the client breathe — if the shoulders rise during inhalation, the scalenes are overworking as primary rather than accessory respiratory muscles.
• In clients with TOS symptoms, the anterior scalene is often significantly tighter on the symptomatic side. Palpation reproduces or exacerbates arm numbness and tingling.
• The scalenes are frequently overlooked in favor of upper trapezius and levator scapulae because they are smaller and deeper. In clients with persistent neck pain that does not respond to upper trapezius and levator scapulae treatment, the scalenes are often the missing piece.

• Use gentle, short-duration sustained compression — 20–30 seconds maximum. The proximity of the brachial plexus means that prolonged pressure risks nerve compression. Monitor for arm paresthesia during treatment.
• Positional release is effective — laterally flex the cervical spine toward the ipsilateral side to shorten the muscle, hold for 60–90 seconds, then slowly return to neutral.
• Diaphragmatic breathing retraining is essential for lasting results. If the client continues chest-breathing, the scalenes will re-tighten regardless of manual treatment.

• The brachial plexus passes between the anterior and middle scalenes. Deep sustained pressure in the interscalene triangle can compress the plexus. Use short-duration techniques and immediately stop if the client reports arm numbness, tingling, or shooting pain.
• The subclavian artery also passes through the interscalene triangle. Excessive pressure can compromise blood flow — monitor for pallor or temperature changes in the hand.
• The phrenic nerve (C3–C5) lies on the anterior surface of the anterior scalene. Compression can produce referred pain to the shoulder tip (C4 referral) and, in extreme cases, diaphragmatic irritation.

• Chronic scalene shortening bilaterally elevates the first ribs and contributes to the "chest-breather" pattern. This reinforces upper crossed syndrome by maintaining shoulder girdle elevation and reducing diaphragmatic excursion. Scalene release combined with diaphragmatic retraining addresses both the muscular and respiratory components.

• If a client presents with arm numbness and tingling that worsens with deep breathing or turning the head, think scalenes before thinking disc. Roos test (elevated arm stress test, or EAST) and Adson's test will help differentiate TOS from cervical radiculopathy. A positive Adson's test with pulse obliteration on the symptomatic side points directly to anterior scalene compression of the subclavian artery.