The shoulder-joint results from the union of the glenoid or shallow cavity on the inferior extremity of the scapula or blade-bone, with the much larger articular surface provided by the head of the humerus or upper arm.

This joint, although so large, possesses only one ligament, the capsular (fig. 352), but it receives the support of a number of muscles which pass over it and are intimately connected with it.

The shoulder-joint is capable of describing a great variety and considerable range of movement. It allows of flexion, extension, abduction, adduction, rotation, and circumduction.

Capsular Ligament of Shoulder Joint.

Fig. 352. - Capsular Ligament of Shoulder-Joint 1, Scapula. 2, Humerus. 3, Capsular Ligament.

Humero radial or Elbow Joint.

Fig. 353. - Humero-radial or Elbow-Joint.

1, Humerus. 2, Radius. 3, Olecranon process of ulna. 4, Arciform ligament. 5, External lateral ligament. 6, Anterior ligament.