Coracobrachialis Muscle

Authors

Affiliations

Nathaniel Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Schematic of Pectoralis major and coracobrachialis¹
1: Pectoralis Major (clavicular part)
2: Pec Major (Sternocostal part)
3: Pec Major (abdominal part)
4: Coracobrachialis

Pectoralis Major and Coracobrachialis, anterior view¹

Muscle	Origin	Insertion	Innervation	Action
Coracobrachialis	Coracoid process	Humerus (in line with crest of lesser tubercle)	Musculocutaneous n. C5 - C7	GHJ: Flexion, Adduction, IR

Origin

Coracoid process of Scapula¹

Insertion

The coracobrachialis inserts on the medial surface of the middle 1/3 of Humerus (in line with crest of lesser tubercle)¹

Innervation

The musculocutaneous n.¹ and (C5¹, C6¹, C7¹) give innervation to the coracobrachialis muscle.

• C5 has mild-mod distribution².
• C6 and C7 have major distribution².

Musculocutaneous n. innervates the muscle as it passes through the muscle³.

Action

Since the coracobrachialis originates from the scapula and inserts on the humerus, it primarily affects the glenohumeral joint (GHJ). The coracobrachialis performs

• GHJ Flexion¹
• GHJ Adduction¹
• GHJ Internal rotation¹

When looking at the shoulder as a whole, the coracobrachialis assists with the first 0-60° of shouulder flexion/elevation since this primarily involves the glenohumeral joint³.

Function

Coracobrachialis serves as a secondary flexor and adductor of the shoulder⁴.

The coracobrachialis is usually recruitted when:

• Scratching your opposite ear⁴.
• Bench press⁴.
• Using your forearm to block in front of your chest during combat sports⁴.

Dysfunction

• Since the musculocutaneous n. passes through the muscle belly, coracobrachialis dysfunction can entrap the nerve and create neurological symptoms³.

Pathologies

Palpation

The coracobrachialis can be found deep to the pectoralis major and Anterior Deltoid. The coracobrachialis is anterior to Axillary artery and brachial plexus, so be mindful when palpating and applying pressure⁴.

Patient position

• Supine⁴.
• 45° GHJ abduction⁴.
• GHJ full external rotation⁴.

Clinician

• Locate pectoralis major (anterior wall of the axilla)⁴.
• Place one hand on the medial arm, just proximal to the elbow⁴.
• Place the fingerpads of the other hand into the axilla⁴.
• Instruct the patient to gently adduct into the non-palpating hand⁴.
• Palpate the inferior medial edge of the pectoralis major, this will act as a reference point⁴.
• Dive posterior to pectoralis major into the axilla⁴.
• Palpate for the “slender” belly of coracobrachialis⁴.
• Active GHJ adduction should cause it to contract⁴.

Checklist

• Is the muscle in the medial arm⁴?
• Is it posterior to pectoralis major⁴?
• Can you strum along the posterior belly⁴?

Manual Muscle Test (MMT)

According to Dale Avers⁵, the coracobrachialis cannot be isolated in a manual muscle test⁵.

It can, however, be tested alongside other muscles in the shoulder flexion MMT⁵.

Weakness

Coracobrachialis weakness can be caused by musculocutaneous n. dysfunction³.

Manual Therapy

1.

Gilroy AM, MacPherson BR, Wikenheiser JC, Voll MM, Wesker K, Schünke M, eds. Atlas of Anatomy. 4th ed. Thieme; 2020.

2.

Neumann DA, Kelly ER, Kiefer CL, Martens K, Grosz CM. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed. Elsevier; 2017.

3.

Dutton M. Dutton’s Orthopaedic Examination, Evaluation, and Intervention. 5th ed. McGraw Hill Education; 2020.

4.

Biel A. Trail Guide to the Body: A Hands-on Guide to Locating Muscles, Bones, and More. 6th ed. Books of Discovery; 2019.

5.

Avers D, Brown M. Daniels and Worthingham’s Muscle Testing: Techniques of Manual Examination and Performance Testing. 10th ed. Elsevier; 2019.