The pectoralis minor is a thin, triangular muscle that lies completely underneath the pectoralis major, connecting the front of the upper ribs to the coracoid process of the shoulder blade. Despite its small size, it exerts a powerful influence on scapular position, pulling the coracoid forward and down, which directly affects how well the shoulder blade can rotate upward during overhead movements. It is a key muscle in both shoulder dysfunction assessment and breathing mechanics.
| Origin | Anterior surfaces and superior borders of ribs 3–5 near their costal cartilages |
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| Insertion | Coracoid process of the scapula |
| Nerve Supply | Medial pectoral nerve (C8, T1) |
| Blood Supply | Pectoral branch of thoracoacromial artery |
| Actions | Protracts and depresses the scapula; Tilts the scapula anteriorly (tips the glenoid downward); Assists forced inspiration by elevating the ribs when the scapula is fixed |
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Its primary role is to stabilise and depress the scapula against the rib cage, but when shortened or hypertonic it becomes a significant contributor to anterior shoulder tipping, limiting the upward rotation needed for full overhead range of motion.
Pectoralis minor tightness is one of the most clinically significant findings in shoulder impingement syndrome, as anterior scapular tipping decreases subacromial space during arm elevation. It can also compress the brachial plexus and subclavian vessels as they pass beneath it, contributing to thoracic outlet syndrome symptoms, numbness, tingling, and heaviness in the arm. Releasing or stretching this muscle is typically a first-line intervention in shoulder rehabilitation.
With the subject supine, slide your fingers under the lower edge of the pectoralis major, angled toward the coracoid process, the pectoralis minor can be felt as a firm cord running diagonally upward. Asking the subject to take a deep breath will cause it to tense slightly.
Compression of the brachial plexus or subclavian vessels beneath a hypertonic pectoralis minor, producing arm pain, paraesthesia, and fatigue with overhead activities, a subset of thoracic outlet syndrome distinguished by tenderness directly over the coracoid attachment.
Muscle fibre tears from sudden forceful protraction or depression of the scapula, presenting as deep anterior chest pain below the clavicle that worsens with reaching forward or deep inspiration.
