306 



THE ARTICULATIONS, OR JOINTS 



V. Elbow-joint (Articulatio Cubiti) (Figs. 248, 249). 



The elbow is a ginglymus or hinge-joint. The bones entering into its forma- 

 tion are the trochlea of the humerus. which is received into the greater sigmoid 

 cavity of the ulna, and admits of the movements peculiar to such a joint viz., 

 flexion and extension; while the capitellum or radial head of the humerus articu- 

 lates with the cup-shaped depression on tHe head of the radius; the circum- 

 ference of the head of the radius articulates with the lesser sigmoid cavity of 

 the ulna, allowing of the movement of rotation of the radius on the ulna, the 

 chief action of the superior radioulnar articulation. The articular surfaces 

 are covered by a thin layer of hyaline cartilage, and connected by a capsular 



FIG. 248. Left elbow-joint, showing anterior 

 and internal ligaments. 



FIG. 249. Left elbow-joint, showing posterior 

 and external ligaments. 



ligament (capsula articularis) (Fig. 250) of unequal thickness, being especially 

 thickened on its two sides and, to a less extent, in front and behind. These 

 thickened portions are usually described as distinct ligaments under the following 



names: 



Anterior. 

 Posterior. 



Internal Lateral. 

 External Lateral. 



