In the first 90 degrees of elevation, which joint provides the majority of scapulothoracic motion?

In the first 90 degrees of arm elevation, the majority of scapulothoracic motion is primarily facilitated by the sternoclavicular joint. This joint serves as the pivotal point connecting the upper limb to the axial skeleton. As the arm elevates, the sternoclavicular joint allows for significant movements, including elevation and protraction of the clavicle. This, in turn, affects the position of the scapula, allowing it to move upward and outward, which is essential for shoulder elevation.

The other joints play important roles in shoulder mechanics, but during the initial phase of elevation, the contribution of the sternoclavicular joint is paramount for proper scapular movement and stabilization. The acromioclavicular joint allows for some upward rotation of the scapula but is more involved in fine-tuning scapular position after the initial elevation has occurred. The glenohumeral joint contributes to the overall motion of the shoulder but does not directly influence the positioning of the scapula in the same way. The scapulothoracic articulation refers to the functional relationship between the scapula and the thoracic rib cage, but it relies on the movements occurring at both the sternoclavicular and acromioclavicular joints to achieve coordinated