ARTICULAR WINDGALL 109 



" dropsical " condition of the synovial capsule of the joint as the 

 result of chronic synovitis. The capsule most commonly affected is 

 that of the fetlock joint. This capsule, it will be remembered, surrounds 

 the articular surfaces of the distal extremity of the large metacarpal 

 bone and the proximal end of the first phalanx. At the back of the 

 joint it extends upwards to supply the articulations formed between 

 the sesamoid bones and the large metacarpal. The joint is not closed 

 in posteriorly by a ligament, as is the case in many joints. Above the 

 sesamoid bone there m^ay be felt a depression which should be noted. It 

 is bounded posteriorly by the branch of the suspensory ligament, anteriorly 

 by the edge of the large metacarpal bone, and superiorly by the button 

 of the splint bone. 



In cases of excessive secretion of synovia the membrane becomes 

 distended. Bulging of the membrane at the front of the joint is 

 prevented by the tendons of the extensor pedis and extensor suffraginis. 

 Lateral bulgings are similarly prevented by the broad and powerful 

 lateral ligaments, whilst the sesamoid bones prevent dilatation of the 

 membrane posteriorly. The membrane distends in the direction of 

 least resistance, with the result that we get at first a filling up of the 

 depressions referred to above, and later a swelling on either side ot the 

 joint immediately in front of the branches of the suspensory ligament. 

 As the condition advances the swellings extend forwards over the lateral 

 aspect of the distal extremity of the large metacarpal bone. 



Articular windgalls are readily diagnosed, since they are in front of 

 the branches of the ligament, whilst tendinous windgalls are situate 

 behind them. 



The affection is attributed to various causes, such as too violent 

 exertion, slipping when jumping, and working animals when immature. 

 They are also said to be due to a looseness in the structure of the fetlock 

 transmitted from sire and dam so affected. 



In the early stages the swellings are easily compressible, and pressure 

 on one leads to a diminution in its size and a corresponding enlargement 



