scapula

The scapula, or shoulder blade, is a large, flat triangular bone located on the posterior thorax. It forms part of the shoulder girdle and serves as the site of attachment for numerous muscles that move the upper limb. The scapula lacks a direct bony articulation with the axial skeleton, instead gliding against the thoracic wall at the scapulothoracic articulation.

Anatomical features include the body, two principal faces (costal anterior and convex posterior), and several processes and borders. The body bears the supraspinous and infraspinous fossae, with the subscapular fossa on the anterior surface. The scapular spine runs across the posterior surface and ends laterally as the acromion, which articulates with the clavicle at the acromioclavicular joint. The coracoid process projects anteriorly and serves as an attachment point for the short head of the biceps brachii, the coracobrachialis, and the pectoralis minor.

The glenoid cavity (glenoid fossa) is a shallow socket on the lateral aspect of the scapula that articulates with the head of the humerus to form the glenohumeral joint. The glenoid is rimmed by the glenoid labrum, which deepens the socket. The scapula has three borders—the medial (vertebral), lateral (axillary), and superior—and three angles: superior, inferior, and lateral. Notable landmarks include the suprascapular notch, the infraglenoid and supraglenoid tubercles, and the coracoid process.

Nerve and vascular supply derive from branches such as the suprascapular nerve and artery, the dorsal scapular vessels, and the subscapular circulation. The scapula provides attachment for the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis), the scapular stabilizers (serratus anterior, rhomboids, trapezius), and others involved in shoulder movement and stabilization.

Clinical notes include scapular fractures being uncommon and scapular winging arising from nerve injury or muscular imbalance.