scapulothoracic

The scapulothoracic articulation is the functional relationship between the scapula (shoulder blade) and the thoracic wall. It is not a true synovial joint, but a functional articulation created by the sliding movement of the scapula over the rib cage, supported by muscles and overlying soft tissues. Movements at this interface are produced by the coordinated action of multiple muscles rather than by a single joint capsule or ligaments.

Anatomy and mechanics: The scapula rests on the anterior surface of the thoracic wall, typically over ribs 2 to 7, and moves on a relatively flat thoracic surface. Muscles that control scapulothoracic motion include the serratus anterior, upper, middle, and lower fibers of the trapezius, the levator scapulae, the rhomboids, and the pectoralis minor. The scapulothoracic articulation contributes to the scapular plane movement and is essential for full upper-limb elevation.

Movements: The primary motions are upward and downward rotation, elevation and depression, protraction (abduction) and retraction (adduction), and anterior and posterior tilting. In arm elevation, the scapula typically undergoes upward rotation and posterior tilt to optimize glenoid orientation and enable greater shoulder range of motion.

Clinical relevance: Dysfunction of scapulothoracic mechanics can lead to scapular dyskinesis, shoulder impingement, or snapping scapula syndrome. Injury to the long thoracic nerve or other stabilizers can produce scapular winging, reducing shoulder stability.

Function: Proper scapulothoracic motion is integral to normal shoulder function, enabling efficient and extensive upper-limb movement through coordinated rhythm with the glenohumeral joint.