998 DISEASES OF THE HOCK. 



Symptoms. (1) Spavin lameness. The diagnosis of arthritis 

 chronica in small, " clean " hocks offers no difficulty, provided disease 

 processes have extended beyond the joint, and exostoses exist. Until 

 they develop, however, diagnosis remains uncertain, for the lameness 

 is not sufficiently characteristic to form the basis of a decided opinion. 

 It is just on this account that errors so frequently occur, and that 

 other lamenesses, even foot-lameness, are mistaken for spavin. But 

 other injuries to the hock, such as sprain, &c, may lead even experts 

 into error. Such mistakes often lead to doubts being cast on the 

 value of treatment. 



The lameness accompanying spavin is scarcely ever sufficiently 

 distinctive alone to determine the diagnosis, but must be considered 

 along with the anatomical changes in the hock-joint. 



Even Knoblock, when speaking of it, says : "If one detects no 

 swelling, how is one to know that a spavin will come ? " One must 

 not be understood to say that the character of the lameness does not 

 afford valuable information, but the kind of lameness is less important 

 than the manner of its appearance and its after-course, and, finally, 

 than the absence of visible pathological changes to which the lameness 

 could otherwise be referred. 



The onset and course of the lameness are, then, of greatest value ; 

 the style of movement, which varies greatly according to the position 

 and extent of the inflammation and to other circumstances, much 

 less so. In the greater number of cases the limb is incompletely 

 extended. The last phase of the stride, while weight is still carried 

 by the limb, is relatively shortened, apparently on account of the pain 

 due to extension of the hock-joint. Immediately the hoof leaves 

 the ground the limb is drawn rapidly forward. This sudden movement 

 often resembles stringhalt, and is best seen during the first few steps, 

 or when turning in a small circle. 



A further consequence of the incomplete extension of the limb 

 is an exaggerated hip-action, which is seldom absent. The 

 shortening of the last part of the stride is compensated by extra 

 movement of the quarter. Sometimes the limb is abducted, especially 

 in double-sided spavin, in which the turning out of the limbs is often 

 well marked. In other cases the fetlock becomes upright, in conse- 

 quence of the incomplete extension of the hock causing the animal 

 when moving over uneven ground to walk on the toe. In almost 

 all established cases the horse wears the toe of the shoe excessively. 



As a rule, lameness develops very gradually. At first it disappears 

 after a few steps, and in many cases all that can be observed is a catch 

 in the movement of the affected limb, resembling stringhalt, when 



