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Scapula (Shoulder Blade): 14 Key Anatomical Facts
The scapula, commonly called the shoulder blade, is a flat triangular bone that connects the upper limb to the axial skeleton. It articulates with the humerus and clavicle, moves in six directions, and serves as an attachment point for 17 muscles enabling arm movement.
A concise explainer of the scapula's anatomy, location, articulations, movements, muscle attachments, and clinical relevance, drawn exclusively from supplied skeletal sources.
Scapula Identity and Classification
The scapula is a flat bone, one of two such bones in the human body, positioned on either side of the upper back between ribs 2 and 7. It forms the pectoral girdle together with the clavicle and manubrium of the sternum, connecting the appendicular skeleton to the axial skeleton.
Scapula Location on the Thoracic Wall
The scapula lies on the upper back of the rib cage, spanning from ribs 2 to 7. It sits between the humerus (upper arm bone) anteriorly and the clavicle superiorly, lying over the posterolateral chest wall.
Articulations with Humerus and Clavicle
The scapula articulates with the humerus at the glenohumeral (shoulder) joint, and with the clavicle at the acromioclavicular joint. These two joints are the primary connections between the upper limb and the trunk.
Six Directions of Scapular Movement
The scapula can move towards the vertebral column (retract), away from it (protract), elevate, depress, and rotate upwards or downwards. These movements are coupled with humeral motion and enable the arm's full range of motion.
Muscle Attachments on the Scapula
Seventeen muscles originate from or insert onto the scapula, including the deltoid, supraspinatus, infraspinatus, teres minor, teres major, latissimus dorsi, coracobrachialis, biceps brachii, trapezius, and serratus anterior. These muscles produce the scapula's six movements and stabilize the shoulder girdle.
Borders and Angles of the Scapula
The scapula has three borders (superior, medial/vertebral, lateral/axillary) and three angles (superior, inferior, lateral). These structural landmarks define its triangular shape and serve as attachment sites for muscles and ligaments.
Surfaces and Fossae of the Scapula
The anterior surface features the subscapular fossa, while the posterior surface is divided by the spine into the supraspinous and infraspinous fossae. The spine ends laterally as the acromion process, which forms the acromioclavicular joint with the clavicle.
Glenoid Cavity and Shoulder Joint Formation
The glenoid cavity, a shallow socket on the lateral angle of the scapula, articulates with the head of the humerus to form the glenohumeral joint. This ball-and-socket joint provides the shoulder's extensive range of motion at the cost of inherent stability.
Coracoid Process and Ligament Attachments
The coracoid process is a curved anterior projection of the scapula that serves as an attachment site for the pectoralis minor, coracobrachialis, and short head of the biceps brachii, as well as several ligaments stabilizing the shoulder girdle.
Scapular Winging and Clinical Relevance
Scapular winging, where the medial border of the scapula protrudes from the thoracic wall, often results from dysfunction of the serratus anterior or long thoracic nerve. It impairs arm elevation and indicates underlying neuromuscular or musculoskeletal pathology.
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