The serratus anterior is the most important scapular stabiliser, holding the medial border of the scapula flat against the thoracic wall and rotating the glenoid upward during arm elevation. Its loss produces the classic medial scapular winging.
| Origin | Outer surfaces of ribs 1-9 — the first rib by a single digitation, ribs 2-4 by separate digitations, ribs 5-9 by interdigitating with the external oblique |
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| Insertion | Costal surface of the medial scapular border — the superior angle (upper slips), medial border, and inferior angle (lower slips) |
| Nerve Supply | Long thoracic nerve (C5, C6, C7) |
| Blood Supply | Lateral thoracic artery and thoracodorsal artery |
| Actions | Protracts the scapula — pulls the scapula around the chest wall; Upwardly rotates the scapula — essential for full arm elevation above 90 degrees; Holds the scapula flat against the thorax |
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Long thoracic nerve injury (from viral illness, stretch, or iatrogenic causes) produces serratus anterior palsy with classic medial scapular winging — the medial border lifts away from the thorax when the arm is elevated. Treatment is conservative — most resolve over 12-24 months. The long thoracic nerve is at risk during axillary lymph node dissection and first rib resection.
Observed as a visible medial border and inferior angle winging during arm elevation or wall push-up.
Medial scapular winging from long thoracic nerve palsy producing inability to fully elevate the arm, managed conservatively with physiotherapy over 12-24 months.
