THE SHOULDER-GIRDLE. 



223 



The ligaments of the joints are inelastic tissues; hence those that enter into the 

 construction of a movable joint must be loose, and the more movable a joint is, the 

 more does its security depend not on its ligaments, but on its muscles. 



The shoulder-joint, like other joints, has a capsular ligament which is attached 

 to the adjacent bones and serves to keep the lubricating synovial fluid applied to the 

 articulating surfaces. In certain positions this ligament may also serve to a limited 

 extent to keep the ends of the bones of the joint in contact. 



Besides this capsular ligament there are fibrous bands which strengthen it at 

 certain places as they pass from adjacent processes of bone on one side of the joint 



Superior acromioclavicular ligament 



Tendon of supra 

 spinatus muscle 



Acromion process 



Clavicle 



Conoid ligament 

 Trapezoid ligament 



oraco-acromial ligament 

 'oracoid process 



Coracohumeral ligament 

 Coracobrachialis muscle 

 Short head of biceps 



Long, head of biceps 



Pectoralis major muscle 



FIG. 236. Acromioclavicular and shoulder joints. 



to those on the other. The muscles and their tendons pass across the capsule and 

 sometimes blend with it, so that there is an intimate relation between the muscles and 

 their tendons and the ligaments; finally, there is a third structure called the glenoid 

 ligament, which is in reality a fibrocartilage that serves to deepen the glenoid cavity. 

 The capsular ligament is attached on one side to the edge of the glenoid cavity, 

 the anatomical neck of the scapula, and the rim of the glenoid ligament. On the 

 other side it is attached above or externally to the anatomical neck of the humerus just 

 at the edge of the articulating surface, but on the lower or inner surface it is attached 

 some distance below the articular surface (approximately i cm.) and then turns 

 upward toward the edge of the articular cartilage. Thus a fracture through the ana- 

 tomical neck might pass outside of the joint above, and inside of it below. The positions 

 assumed by the capsule in abduction and adduction are shown in Figs. 237 and 238. 



