The coracobrachialis connects the coracoid process to the mid-humerus, producing shoulder flexion and adduction. The musculocutaneous nerve pierces through the coracobrachialis muscle (or less commonly passes anterior to it) to enter the anterior arm compartment — this is the anatomical definition of the coracobrachialis as a surgical landmark for finding the musculocutaneous nerve.
| Origin | Apex of the coracoid process (alongside the short head of biceps) |
|---|---|
| Insertion | Medial surface of the mid-humerus shaft |
| Nerve Supply | Musculocutaneous nerve (C6, C7) — the nerve pierces through this muscle |
| Blood Supply | Brachial artery |
| Actions | Flexion of the arm at the shoulder; Adduction of the arm |
|---|
Coracobrachialis is a weak shoulder flexor that functions primarily to stabilise the glenohumeral joint in flexion rather than generating significant motion. Its adduction function helps maintain the arm close to the body during arm swing in walking.
Isolated coracobrachialis pathology is rare but can produce anterior shoulder and upper arm pain reproduced by resisted shoulder flexion and adduction. The musculocutaneous nerve can be compressed within the coracobrachialis during repeated arm movements, producing lateral forearm numbness from lateral antebrachial cutaneous nerve irritation.
The coracobrachialis is palpable in the axilla and proximal medial arm by deep pressure, becoming firm during resisted shoulder adduction from the flexed position.
Anterior shoulder and upper arm pain from coracobrachialis overload reproduced by resisted shoulder flexion-adduction managed conservatively.
