The Scapula

The scapula is a large, flat, triangular bone on the posterolateral aspect of the thoracic wall, overlying ribs 2–7. It connects to the humerus at the glenohumeral joint and to the sternum indirectly via the clavicle.

Surfaces (2)

Costal (anterior/ventral) surface Dominated by the subscapular fossa — a broad concavity where the subscapularis muscle originates. Oblique ridges give attachment to the fibrous intramuscular septa of subscapularis. A narrow strip along the medial edge is the attachment of serratus anterior (which keeps the scapula pressed against the thorax).

Dorsal (posterior) surface Divided into two asymmetric regions by the spine of the scapula:

Supraspinous fossa (smaller, superior) — origin of supraspinatus
Infraspinous fossa (larger, inferior) — origin of infraspinatus (medially), teres minor (superolateral), and teres major (inferolateral) The two fossae communicate via the spinoglenoid notch between the dorsal scapular neck and the lateral border of the spine.

Borders (3)

Border	Course	Key Attachments
Superior	Concave; from superior angle to coracoid base	Inferior belly of omohyoid; contains the suprascapular notch (bridged by the transverse scapular ligament, through which the suprascapular nerve passes)
Medial (vertebral)	Longest; from superior to inferior angle	Levator scapulae (upper), rhomboid minor (mid), rhomboid major (inferior)
Lateral (axillary)	From inferior glenoid margin to inferior angle	Infraglenoid tubercle at its superior end; separates subscapularis, teres minor, and teres major

Angles (3)

Lateral angle — marked by the glenoid cavity, a shallow comma-shaped socket that articulates with the humeral head (glenohumeral joint). Articular surface = ~6–8 cm², about one-third to one-fourth the size of the humeral head; retroverted ~4–8°.
Superior angle — at the junction of the superior and medial borders
Inferior angle — palpable landmark at the bottom of the bone, at ~T7–T8; the reference point clinically for scapular winging

Processes (3)

Spine A triangular, plate-like posterior projection. Broadens and elevates laterally to become the acromion. Trapezius inserts on its superior surface; deltoid originates from its inferior surface.

Acromion The lateral continuation of the spine, forming the roof of the glenohumeral joint. Articulates with the clavicle at the acromioclavicular (AC) joint. Can be flat (type 1) or curved (type 2). Os acromiale — failure of the acromial ossification center to fuse by age 25 (7–15% of individuals); clinically associated with shoulder impingement.

Coracoid process A hook-like projection arising from the superior border of the neck that curves anteriorly and laterally over the glenoid. Attachment site:

Apex: short head of biceps brachii + coracobrachialis
Medial surface: pectoralis minor
Base (lateral): coracohumeral ligament
Superior surface: conoid and trapezoid ligaments (coracoclavicular ligaments connecting to clavicle) The coracoacromial ligament spans from the coracoid to the acromion, completing the coracoacromial arch above the rotator cuff.

Glenoid Landmarks

Landmark	Location	Attachment
Supraglenoid tubercle	Just superior to glenoid	Long head of biceps brachii (intra-articular)
Infraglenoid tubercle	Inferior to glenoid, on scapular neck	Long head of triceps brachii (extra-articular)
Glenoid notch	Ventral margin of glenoid	Present in ~55% of scapulas

Muscular Attachments — Summary

Origins from scapula: subscapularis, supraspinatus, infraspinatus, teres minor, teres major, long heads of biceps and triceps, short head of biceps, coracobrachialis, pectoralis minor, omohyoid, serratus anterior (insertion)

Insertions onto scapula: trapezius (spine/acromion), levator scapulae (medial border), rhomboid major & minor (medial border), serratus anterior (medial border, costal surface)

Nerves of the Scapular Region

Nerve	Origin	Key point
Suprascapular nerve	C5–C6 (upper trunk)	Passes through the suprascapular notch under the transverse scapular ligament; supplies supraspinatus and infraspinatus
Long thoracic nerve	C5–C7 (roots)	Runs on external surface of serratus anterior along lateral chest wall; vulnerable in axillary dissection (e.g. mastectomy)
Dorsal scapular nerve	C5 root	Supplies rhomboids and levator scapulae
Axillary nerve	C5–C6	Passes through quadrilateral space; supplies deltoid and teres minor

Winged Scapula

Damage to the long thoracic nerve paralyses serratus anterior, causing the medial border and inferior angle to protrude posteriorly — classic "winging." This is accentuated when the patient pushes against a wall or raises their arms. It is the most common complication of axillary lymph node dissection (e.g. radical mastectomy).

Joints

Joint	Bones	Type
Glenohumeral	Glenoid cavity + humeral head	Synovial ball-and-socket; most mobile joint in body
Acromioclavicular (AC)	Acromion + lateral clavicle	Synovial plane
Scapulothoracic	Scapula + thoracic wall	Physiological joint (gliding); not a true synovial joint

Illustrated Anatomy

Anterior view — bony landmarks & muscle attachments:

Anterior view of the left scapula showing subscapular fossa, borders, angles, glenoid cavity, coracoid process, and muscle attachments

Posterior/lateral views — spine, fossae, processes:

Superior and lateral views of the left scapula showing the spine, supraspinous and infraspinous fossae, spinoglenoid notch, suprascapular notch, and glenoid cavity

Posterior muscle attachments:

Posterior view showing muscle attachments including infraspinatus, trapezius, rhomboid major, teres minor, teres major, and latissimus dorsi

Sources: Gray's Anatomy for Students; Imaging Anatomy: Bones, Joints, Vessels and Nerves, Vol. 3

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