Scapulothoracic joint

The scapulothoracic joint movements are related to scapular motions. The motions are medial and lateral movements of the scapula on the thorax (abduction-adduction), elevation of the scapula, and upward and downward rotation of the scapula (tilt), all relative to the glenoid fossa. 

The two functional joints in the shoulder girdle are the suprahumeral joint and the scapulothoracic joint. As mentioned, both figure prominently in shoulder biomechanics and pathology. The suprahumeral joint is formed by the articulation of the head of the humerus with the coracoacromial arch, composed of the acromion, the coracoid process, and the ligament between them. Articulation occurs during abduction. 

The second functional joint is the scapulothoracic joint. This is formed by the scapula and the posterior thorax (ribs). Because muscle and fascia lie between the articulating surfaces, it is not a true joint with approximated articular surfaces and is also lacking a capsule. 

The shoulder complex consists of four distinct articulations the glenohumeral joint, the acromioclavicular joint, the sternoclavicular joint, and the scapulothoracic articulation. The wide range of motion of the shoulder (exceeding a hemisphere) is the result of synchronous, simultaneous contributions from each joint The most important function of the shoulder is arm elevation. Several investigators have attempted to relate glenohumeral and scapulothoracic motion during arm elevation in various planes... 

Table 49.13). About two-thirds of the motion takes place in the glenohumeral joint and about one-third in the scapulothoracic articulation, resulting in a 2 1 ratio. 

Clinical Anatomy 190 Osseous and Articular Anatomy 190 Glenohumeral Joint 190 Acromioclavicular Joint 191 Sternoclavicular Joint 193 Scapulothoracic Plane 193 Muscles and Tendons 193 Rotator Cuff 193... 

---