REGION OF THE ELBOW. 



287 



SURFACE ANATOMY. 



Having become acquainted with the bones and muscles, one will be better able 

 to appreciate the surface markings and understand their significance (Fig. 299). 



When the elbow is fully extended the bony projections are obscured by the soft 

 tissues, hence in examining an elbow it should be flexed at approximately a right 

 angle. The first object to strike the eye is the prominent olecranon process. It is 

 subcutaneous and the bony ulna beneath can be felt and followed down the back of 

 the forearm. From the tip upward for a couple of centimetres can be felt the upper 

 surface of the olecranon into which the triceps inserts. To feel this distinctly the 

 forearm should be slightly extended to relax the triceps; the outline of the upper 

 portion of the olecranon then becomes perfectly distinct. 



Projecting on each side of the elbow are the two condyles of the humerus. 

 These bony projections do not belong to the forearm. The two condyles are nearly 

 on the same level. The medial (internal) is much more prominent and has the 

 appearance of being a trifle higher and slightly anterior. A line joining them 



Tendon of triceps 



Internal condyle 

 Olecranon process 



Flexor carpi ulnaris 



Brachioradialis and extensor carpi 

 radialis longior 

 External condyle 



Depression, head of radius 

 Anconeus 



Extensor communis digitorum 

 Extensor carpi ulnaris 

 Subcutaneous surface of ulna 



FIG. 299. Surface anatomy of the back of the elbow. 



crosses the long axis of the humerus at an angle of 90 degrees, but makes an angle 

 of only 80 degrees with the forearm. By deep pressure the lateral (external) supra- 

 condylar ridge can readily be felt running up the arm somewhat posteriorly from 

 the lateral (external) condyle. The medial (internal) supracondylar ridge is much 

 less easily felt though the intermuscular septum is more evident on this side. When 

 the elbow is flexed at a right angle a line drawn parallel with the humerus and joining 

 the two condyles will pass through the tip of the olecranon. If the forearm is 

 extended the olecranon passes slightly posterior to this line; if the forearm is flexed, 

 the olecranon passes somewhat in front of it. Hence in examining the elbow for 

 injury it is desirable to determine the relation of these points when the elbow is bent 

 at a right angle. The coronoid process lies anteriorly, deep in the flexure of the 

 elbow, and cannot be distinctly felt. 



If, now, the elbow is extended, the tip of the olecranon can still be felt with the 

 medial (inner) condyle to its inner side. Between the two is a deep groove in which 

 lies the ulnar nerve. To the outer side of the olecranon is a deep pit or short groove; 

 the bone marking its outer edge is the lateral (external) condyle. In the bottom of 

 this pit at its lower portion, about 2. 5 cm. ( i in. ) below the tip o* the olecranon, can 

 be felt the head of the radius. If the thumb is placed on it and the hand rotated, the 



