Introduction Function allows scapular motion against the rib cage Osteology not a true joint; actually an articulation between the scapula and the thorax is a sliding "joint" between medial border of scapula and ribs 2-7 resting position angulation (although these are variable even in healthy adults) anteriorly 10-20° internally rotated 30°-45° from the coronal plane upward tilt of 3° Biomechanics Motion primary motion elevation & depression movement up and down along the rib cage secondary motions protraction & retraction movement away from or toward the vertebral column upward & downward rotation upward rotation with arm elevation downwared rotation with arm returning to side from raised position internal & external rotation anterior & posterior tipping shoulder abduction the ratio of glenohumeral motion to scapulothoracic motion is 2:1 GH does 120°, then ST does 60° Stability 17 different muscles attach to or originate from the scapula trapezius serratus anterior deltoid latisimus dorsi levator scapulae rhomboid major rhomboid minor omohyoid - inferior belly pectoralis minor teres major teres minor triceps brachii biceps brachii coracobrachialis infraspinatus subscapularis supraspinatus Clinical Scapulothoracic dissociation Scapular winging Scapulothoracic dyskinesis