182 



THE ARTICULATIONS OF THE HORSE 



The external lateral ligament (Ligamentum collaterale ulnare) is short and 

 strong. It is attached above to a depression on the external epicondyle of the 

 humerus, and below to the external tuberosity of the radius, just below the margin 

 of the articular surface. 



Movements. — This joint is a typical ginglymus, the only movements being 

 flexion and extension around an axis which passes through the upper attachments 

 of the lateral ligaments. In the standing position the articular angle (in front) is 

 about 140° to 150°. The range of movement is about 55° to 60°. Complete ex- 

 tension is prevented chiefly by the tension of the lateral ligaments and the biceps 

 muscle. (The axis of movement is slightly oblique, so that in flexion the forearm 

 is carried somewhat outward.) 



External 



lateral - - 

 ligament 



Metacarpal < ^^^ 



tuberosity 



External dis- 

 tal tuberosity 

 of radius 



Accessory 

 carpal bone 



Inferior liga- 

 ments of ac- 

 cessory car- 

 pal 



External 



metacarpal 



bone 



Fig. 144. — Left Carpal Joints of Horse, Exter- 

 nal View 

 The capsule has been removed, g. Radius; 12, 

 large metacarpal bone. (After EUenberger-Baum, 

 Anat. f. Kiinstler.) 



Internal dis- 

 tal tuberosity 

 of radius 



Internal 



lateral 



ligament 



Metacarpal 

 tuberosity ~ 



-External dis- 

 tal tuberosity 

 of radius 



External 

 lateral 

 ligament 



.External 

 metacarpal 

 bone 



Fig. 145. — Left Carpal Joints of Horse, Anterior 

 View. 

 The capsule has been removed. The smaller liga- 

 ments are shown. (After EUenberger-Baum, Anat. 

 f. Kiinstler.) 



THE RADIO-ULNAR ARTICULATION 



In the foal the shaft of the ulna is attached to the radius above and below the 

 interosseous space by the interosseous ligament. Below the space the two bones 

 become fused before adult age is reached. Above the space the ligament usually 

 persists, but may undergo more or less ossification in extreme old age. The 

 transverse or arciform ligaments (Ligamentum transversum ulnare et radiale 

 ulniB et radii) consist of fibers which pass above the interosseous space from either 

 border of the shaft of the ulna to the posterior surface of the radius. The proximal 

 radio-ulnar articulation, formed by two small convex facets on the ulna and the 

 corresponding facets on the posterior surface of the proximal extremity of the radius, 

 is inclosed in the capsule of the elbow-joint and does not require separate consider- 

 ation. The distal extremity of the ulna fuses early with the radius, and is, there- 

 fore, regarded usually as a part of the latter. 



Movement. — This is inappreciable, the forearm being fixed in the position of 

 pronation. 



