STIFF JOINTS. 



273 



are straightened out ; loss of " play " in the fetlock joint (or 

 uprightness of pastern) is always followed by more or less 

 loss of power of locomotion. In light saddle-horses which 

 are sound and which have good action, the fetlock pad, in 

 the gallop or fast canter, should come nearly down to the ground, 

 as in Fig. 11 (p. 39), in which the pastern makes an angle of 

 about 120° with the cannon bone. The maximum direct flexion 

 (bending) of a healthy fetlock joint is shown in Fig. 103. 



Fig. I02. — Alternate position assumed in rheumatoid arthritis of stifle. 



As a rule, when inflammation from work or sprain (which are 

 the cases we are at present considering) occurs in a joint sufli- 

 ciently to permanently impair its power of movement, we shall 

 find adhesions about the part, and, probably also, shortening of 

 the ligaments which antagonise the extension of the joint, and 

 which, in the case of the fetlock, check the descent of the fetlock 

 pad. The further progress of these cases will generally be depo- 

 sition of bone about the part, and the gradual conversion into 

 bone of the fibrous structm'es and cartilages of the joint. A 

 return to soundness is possible only when the articular cartilages 

 (p. 269) have remained intact, and when any bony deposit which 

 may have taken place, is so situated as not to interfere with the 

 movement of the joint. At the same time, our surgical interfer- 

 ence need not be restricted to obtaining soundness; but may also 



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