THE ELBOW-JOINT 137 



olecranon, between the tendon of the triceps and the bone; 

 (3) at the inner margin of the brachialis anticus; (4) bicipital 

 bursa, between the tendon of the biceps and the bone; (5) 

 epicondylar bursse, subcutaneous; (6) sometimes a retro- 

 epitrochlear behind the inner epicondyle, related to the ulnar 

 nerve. 



Nerves are from the ulnar, median, musculospiral, internal 

 cutaneous, and nerve of Cruveilhier (from the branch of the 

 musculocutaneous to the biceps). 



Arteries are derived from an anastomosis between the inferior 

 and superior profunda, anastomotica magna, anterior and 

 posterior ulnar recurrent, interosseous recurrent, and radial 

 recurrent. 



Action. The humeroulnar joint possesses flexion and exten- 

 sion, no lateral movement or rotation. 



Flexion of 150 degrees is possible, produced by the supinator 

 longus, biceps, brachialis anticus, and muscles from the inner 

 condyle; it is checked by contact of soft parts, posterior part 

 of the capsule, and posterior part of the internal and external 

 lateral ligaments, not by bone. 



Extension (after flexion) goes through 150 degrees by the 

 triceps, anconeus, extensors of the wrist, and common extensors 

 of the ringers; it is checked by the anterior part of the capsule 

 and anterior parts of the external and internal lateral liga- 

 ments, not by bone. 



Supination (rotation out) and pronation (rotation in) occur 

 through 90 degrees in the radioulnar and radiohumeral joints 

 on an axis through the head and neck of the radius and styloid 

 process of the ulna. Supination is performed by the biceps 

 strongly, by the supinator longus and brevis and extensors 

 of the thumb; pronation by the pronator radii teres and pro- 

 nator quadratus; in this last motion there is a "winding up" 

 of the biceps and supinator brevis. These rotary movements 

 are checked by the oblique ligament, orbicular, and capsular, 

 by the interosseous membrane, by the inferior articulation, 

 and by muscles. If sliding of the soft parts on the ulna is 

 hindered, pronation and supination are largely checked. 



