<P> In humans, the only true anatomical joints between the shoulder girdle and the axial skeleton are the sternoclavicular joints on each side . No anatomical joint exists between each scapula and the rib cage; instead the muscular connection or physiological joint between the two permits great mobility of the shoulder girdle compared to the compact pelvic girdle; because the upper limb is not usually involved in weight bearing, its stability has been sacrificed in exchange for greater mobility . In those species having only the scapula, no joint exists between the forelimb and the thorax, the only attachment being muscular . </P> <P> The shoulder girdle is a complex of five joints that can be divided into two groups . Three of these joints are true anatomical joints while two are physiological ("false") joints . Within each group, the joints are mechanically linked so that both groups simultaneously contribute to the different movements of the shoulder to variable degrees . </P> <P> In the first group, the scapulohumeral or glenohumeral joint is the anatomical joint mechanically linked to the physiological subdeltoid or suprahumeral joint (the "second shoulder joint") so that movements in the latter results in movements in the former . In the second group, the scapulocostal or scapulothoracic joint is the important physiological joint that cannot function without the two anatomical joints in the group, the acromioclavicular and sternoclavicular joints, i.e. they join both ends of the clavicle . </P> <P> The glenohumeral joint is the articulation between the head of the humerus and the glenoid cavity of the scapula . It is a ball and socket type of synovial joint with three rotatory and three translatory degree of freedom . The glenohumeral joint allows for adduction, abduction, medial and lateral rotation, flexion and extension of the arm . </P>

Both the clavicle and the scapula are bones of the shoulder girdle