414 THE ANATOMY OF THE HORSE 



4. The ligaments common to the avhole knee joint are four — two 

 lateral, an anterioi', and a posterior. 



The external lateral Vuiament is a thick cord, formed of two kinds of libres, 

 a deep-seated and a superficial set, which take a crucial direction. It arises 

 from the external lateral process of the radius, and descends vertically on 

 the side of the knee joint. In its passage, it gives off a band to th(^ 

 pisiform bone, and also to the os unciforme, and terminates at the head of 

 the external small metacarpal bone. This ligament lies on the carpal bones 

 and capsular ligament. 



The internal lateral ligament, analogous to the preceding, and situated on 

 the opposite side, is thicker and larger. It arises from the internal lateral 

 process of the radius, and terminates on the supero-antei'ior and internal 

 surface of the large metacarpal and head of the internal small metacarpal 

 bones. The fibres of this ligament take a crucial direction ; in its passage 

 downwards, it gives off three little bands, namely, one to the scaphoid bone, 

 one to the os magnum, and one to the trapezoid. 



The anterior or capsular ligament covers the anterior face of the carpal 

 articulations. Its superior edge is attached to the inferior extremity of 

 the radius ; its inferior edge is attached to the superior extremity of the 

 large metacarpal bone ; its right and left borders are in contact with the 

 lateral ligaments ; its external face is connected with tendons, etc. ; its 

 internal face is lined, at certain points, by synovial membrane. This 

 ligament is formed of transverse fibres, more or less oblique, crossed and 

 i-e-crossed. 



The posterior ligament — one of the strongest of the animal economy — 

 covers the posterior surface of the knee. It is inserted superiorly into the 

 transverse ridge which bounds the articular surface of the i^adius. At the 

 posterior part of the carpal bones, it becomes attached to the inner border 

 of the pisiform bone, the posterior sui'face of the os magnum, the cuneiform 

 and scaphoid bones terminating on the postero-superior extremity of the 

 large metacarpal bone. The scapho-metacarpal ligament, described as part 

 of the posterior ligament of the carpo-metacarpal joint, is with difficulty 

 separated from this ligament. 



The knee is the centre of two very extensive movements, namely, 

 extension and flexion ; to which three others, very limited in their extent, 

 may be added, namely, adduction, abduction, and circumduction. 



As already mentioned, all the carpal articulations do not take an equal 

 part in the execution of these movements ; in fact, it is evident that they 

 chiefly take place in the radio-carpal ginglymus, and in the imperfect hinge 

 formed between the two rows of carpal bones. Each of these articulations 

 participates in the movements of the knee, nearly in the same joroportion, 

 the superior perhaps being slightly the more extensive, and both perform 

 their office in the same manner. 



In flexion, the first row of bones turns from before backwards on the 

 radius ; the inferior row moves in the same way on the superior i*ow. The 

 metacarpus is carried backwards and upwards, thus relaxing the common 

 posterior ligament. The anterior ligament, on the contrary, is rendei-ed 

 tense. The articular surfaces, especially those of the second joint, separate 

 in front from one another. 



In extension, the metacarpus is carried below and forwards by an inverse 



