KNUCKLING AT THE FETLOCK. 851 



V.~ KNUCKLING AT THE FETLOCK IN FOALS. 



In thoroughbred stock, less frequently in other breeds, foals at 

 birth are sometimes unable to move properly owing to excessive 

 knuckling of the fore or hind fetlocks. Three degrees of knuckling 

 are recognised : (1) the cannon and pastern are in the same line, the 

 angle of the fetlock being effaced ; (2) the fetlock is carried forward, 

 forming an angle open behind ; (3) the fetlock is projected forwards 

 beyond a vertical line rising from the toe of the foot. 



The upright position of the fetlock prevents the flexors taking 

 their proper part in sustaining weight. This peculiar deformity 

 generally affects both fore legs, often causing the animals to walk 

 with the front of the phalanx on the ground and preventing their 

 standing upright. It also develops, though rarely, during the first 

 two or three years of life, but never in such a serious form. 



The cause has not been satisfactorily explained. Knuckling 

 in foals has been attributed to infection derived from the mare during 

 gestation or contracted soon after birth, to myositis of the flexors 

 of the foot, and, when knuckling is associated with bent knees, to 

 myositis of the flexors of the metacarpus. Frdhner mentions that 

 congenital cases are often clue to weakness of the extensors, and 

 some breeders from observation of the produce of certain stallions 

 regard the condition as hereditary. Franck considers it due to 

 congenital contraction of the flexor tendons existing at the time of 

 birth. Others ascribe it to abnormal position of the foetus in utero, 

 whilst Lafosse thinks it arises from disproportion between the 

 stallion and mare, the bony framework being excessively developed 

 when the stallion is too large. As large animals are especially affected, 

 and as, in general, only the phalanges suffer displacement, the cause 

 must lie between the point of insertion of the flexor perforans and its 

 reinforcing ligaments. There are two possibilities : either the 

 tendons are too short or the metcarpus is too long. The first may be 

 referred either to defective development or subsequent shortening 

 of the tendons. Whether, in such case, the development of the 

 flexor tendons is interfered with by the position of the foetus in utero, 

 or whether contraction occurs, or whether the long axis of the meta- 

 carpus is excessively developed, so that the tendons are relatively 

 too short, or whether again the point of origin of the muscles is 

 abnormal, is for the time at least undecided. Perhaps the condition 

 may be caused in more than one way. 



Abnormal position in utero would probably interfere with 

 development of the joints and muscular tissue. Increase of pressure 



