136 ARTHROLOGY, OR ANATOMY OF ARTICULATIONS 



surface. The lowest fibers are transverse, bridging over part 

 of the olecranon fossa; the upper fibers are vertical, thickest 

 in the median line, and pass through a fatty pad in the upper 

 part of the fossa. These vertical fibers are Barkow's posterior 

 straight cubital ligament; on either side of it the capsule is as 

 thin as a bursa. 



The internal lateral ligament is fan-shaped, rises from the 

 lower and back part of the root of the inner epicondyle, and 

 consists of three portions: (1) A posterior humeroolecranon 

 part, helping form the groove for the ulnar nerve ; (2) an anterior 

 humerocoronoid part; and (3) an olecranocoronoid portion, 

 deepening the sigmoid cavity. 



The external lateral ligament is not so distinct as the internal; 

 it is attached above to a depression below the external epi- 

 condyle, and below to the orbicular ligament and to the upper 

 part of the interosseous border of the ulna (not into the radius, 

 or its rotation would be impaired). It gives some strengthening 

 bands to the anterior ligament, forming a cruciform arrange- 

 ment. The supinator brevis arises from this ligament in part, 

 The brachialis anticus muscle inserts a band into the anterior 

 ligament, the triceps a band into the posterior. The anconeus 

 arises partly from the capsule between the external condyle 

 and external border of the olecranon. 



The orbicular ligament is described under the superior radio- 

 ulnar articulation. 



The synovial membrane is extensive, lines the capsule and 

 orbicular ligament, and enters into the articulation between 

 all three bones. 



There are inequalities between the sigmoid fossa and trochlea 

 which are "filled in with synovial membrane or fatty pads; 

 there is another pad in the small sigmoid cavity. The capsule 

 is reinforced by intracapsular and extracapsular pads, both 

 in the coronoid and olecranon fossae. This allows free gliding 

 of muscles. The triceps pulls up the wrinkled capsule in 

 extension, the brachialis anticus in flexion. 



The muscles in relation to the joint are, in front, the brachialis 

 anticus; behind, the triceps and anconeus; externally, the 

 supinator brevis and supinatoextensor group; internally, the 

 pronatoflexor group. 



The bursae related to the joint are: (1) Superficial olecranon 

 bursa between the tendon of the triceps and the skin; (2) deep 



