Coracobrachialis

Origin, Insertion, Action, Innervation

Origin: Coracoid process of the scapula (with the short head of biceps brachii and pectoralis minor)
Insertion: Medial surface of the mid-shaft of the humerus (approximately at the level of the deltoid tuberosity)
Action:
Primary: Flexion of the shoulder (weak)
Adduction of the shoulder (weak)
Horizontal adduction of the shoulder (weak)
Stabilization of the glenohumeral joint during abduction (resists inferior dislocation)
Innervation: Musculocutaneous nerve (C5–C7) — the nerve pierces through the muscle belly

Palpation Guide

Client position: Supine with the arm slightly abducted and externally rotated to open the medial arm.
Landmark sequence:

Locate the short head of biceps brachii in the proximal arm. Coracobrachialis lies deep and medial to the short head, sharing the coracoid process origin.
With the client's arm slightly abducted, palpate the medial aspect of the proximal arm, pressing gently posterior to the biceps short head. Coracobrachialis is felt as a thin, rope-like muscle running from the axilla toward the mid-humerus.
The muscle is most palpable in the proximal third of the arm where it emerges from beneath the anterior deltoid before being overlapped by biceps.
To confirm the coracoid process attachment, palpate the coracoid by pressing approximately 2 cm inferior and lateral to the clavicle at the junction of the lateral and middle thirds — it is deep and tender. Three structures attach here: coracobrachialis, short head of biceps, and pectoralis minor.

Tissue feel: Thin and cord-like compared to the bulky biceps. Feels like a firm band running along the medial proximal arm. The coracoid process origin is deep and requires firm pressure through the anterior deltoid.
Confirmation test: Ask the client to horizontally adduct the arm (bring the arm across the chest) against light resistance. You will feel the muscle firm up along the medial proximal arm. It is a weak muscle, so contraction is subtle compared to the pectorals and biceps.
Common errors:
Confusing coracobrachialis with the short head of biceps — they share the coracoid process origin and run together in the proximal arm. Coracobrachialis inserts on the mid-humerus and does not cross the elbow; biceps continues distally.
Pressing too aggressively in the medial proximal arm — the brachial artery, median nerve, ulnar nerve, and musculocutaneous nerve are all in this area. Palpate gently.
Expecting a large, distinct muscle belly — coracobrachialis is small and thin. It does not have the prominent contour of other arm muscles.

Trigger Point Referral

Common TrP locations: The TrP is located in the mid-belly of the muscle along the medial proximal arm, approximately at the level where the musculocutaneous nerve exits the muscle.
Referral pattern: Refers to the anterior deltoid region, the posterior arm along the triceps, and distally to the dorsum of the forearm and hand (back of the hand between the thumb and index finger).
Clinical significance: The dorsal hand referral is unexpected from a proximal arm muscle — it can be mistaken for C6 radiculopathy or radial nerve involvement. If dorsal hand symptoms do not correlate with cervical or radial nerve tests, palpate coracobrachialis.

Trigger point referral diagram — coming soon

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

Clinical Notes

Innervation significance:

The musculocutaneous nerve pierces through the coracobrachialis muscle belly — this is a potential entrapment site. Hypertonic or fibrotic coracobrachialis can compress the musculocutaneous nerve, producing weakness in elbow flexion (biceps and brachialis) and sensory changes over the lateral forearm (lateral cutaneous nerve of forearm territory). This is rare but clinically important when anterior arm symptoms do not match other diagnoses.

Common conditions:

Coracoid process tenderness — the coracoid is a shared attachment for coracobrachialis, short head of biceps, and pectoralis minor. Tenderness at the coracoid can arise from any of these structures. Differentiate by resisted testing: horizontal adduction and shoulder flexion with adduction stresses coracobrachialis; resisted elbow flexion/supination stresses biceps short head; the pectoralis minor stretch test stresses pectoralis minor.
Involved in conditions/upper-crossed-syndrome — as part of the anterior shoulder muscle group, coracobrachialis can shorten with chronic protracted posture, contributing to the rounded-shoulder pattern.
The coracoid process is a key landmark in conditions/thoracic-outlet-syndrome — the neurovascular bundle passes inferior to the coracoid during shoulder hyperabduction.

What you'll typically find:

Coracobrachialis is rarely the primary complaint muscle, but it is frequently tender when assessed. In clients with chronic shoulder protraction or habitual arm-crossing postures, the muscle is shortened and fibrotic.
Tenderness at the coracoid process is common and nonspecific — students must differentiate which of the three coracoid muscles is involved rather than simply labeling it "coracoid pain."

Treatment effects:

Responds to gentle sustained compression and short stripping strokes along the medial proximal arm. The muscle is small and does not tolerate aggressive deep tissue techniques.
Release often produces an immediate sense of "openness" in the anterior shoulder — clients describe the shoulder feeling lighter or less pulled forward.

Cautions:

The brachial artery, median nerve, and ulnar nerve all pass through the medial arm in close proximity to coracobrachialis. The axillary artery pulse is palpable in the axilla just lateral to the muscle. Use light to moderate pressure only and monitor for arterial pulsation.
The musculocutaneous nerve pierces through the muscle — sustained heavy compression could irritate the nerve within the muscle. If the client reports tingling or numbness in the lateral forearm during treatment, reduce pressure.
Deep pressure toward the coracoid process requires care — the coracoid is deep to the anterior deltoid and lies just superior to the axillary neurovascular bundle.

Clinical pearl:

Coracobrachialis is the small muscle that tells a big story. If you find it significantly hypertonic and tender, it usually means the entire anterior shoulder complex is shortened — check pectoralis minor, biceps short head, and subscapularis as well. Coracobrachialis is the canary in the coal mine for anterior shoulder dysfunction.

Assessment

Manual muscle testing:

Shoulder flexion with adduction: Client supine. Arm flexed to approximately 60–70 degrees and slightly adducted across the body. Apply resistance into extension and abduction. This position minimizes anterior deltoid contribution and emphasizes coracobrachialis.

Stretch test:

Shoulder extension with slight abduction: Client seated or supine. Extend the shoulder (arm behind the body) with slight abduction and external rotation. Tightness in the anterior proximal arm suggests coracobrachialis shortening. Compare bilaterally.

Related special orthopedic tests:

No specific SOTs target coracobrachialis in isolation. Coracoid tenderness is assessed during shoulder examination and differentiated by resisted testing as described in Clinical Notes.

Muscle Groups

Shoulder flexors (functional — weak role):

anatomy/muscles/biceps-brachii — long head
Coracobrachialis (this article)
Anterior deltoid (primary)

Coracoid process attachment group (anatomical):

Coracobrachialis (this article)
anatomy/muscles/biceps-brachii — short head
Pectoralis minor

Musculocutaneous nerve group (innervation):

Related Muscles

Synergists for shoulder flexion:

anatomy/muscles/biceps-brachii — long head; also crosses the elbow
Anterior deltoid — primary shoulder flexor

Synergists for shoulder adduction:

anatomy/muscles/latissimus-dorsi — powerful adductor and extensor
Pectoralis major — powerful adductor and horizontal adductor
Teres major — adductor and internal rotator

Antagonists:

Posterior deltoid — shoulder extensor
Middle deltoid — shoulder abductor (opposes adduction)

Same innervation (musculocutaneous nerve):

anatomy/muscles/biceps-brachii — C5–C6
anatomy/muscles/brachialis — C5–C6

Key Takeaways

The musculocutaneous nerve pierces through coracobrachialis — hypertonic tissue here can entrap the nerve, producing elbow flexion weakness and lateral forearm sensory changes.
The TrP refers unexpectedly to the dorsum of the hand — mimicking C6 radiculopathy or radial nerve involvement.
Coracobrachialis tenderness is a sentinel for broader anterior shoulder shortening — always assess pectoralis minor, biceps short head, and subscapularis when coracobrachialis is involved.