112 THE SURGICAL ANATOxMY OF THE HORSE 



and not infrequently the condition leads ultimately to anchylosis of the 

 long with the short pastern bone. 



There is considerable divergence of opinion as to the exact seat of 

 origin of true ringbone. Some maintain that it commences as a chon- 

 dritis in which the articular cartilage is affected. Others state that the 

 seat of origin is the synovial membrane, and that the condition 

 commences as a synovitis and extends to the cartilage. Post-mortem 

 specimens may be found to support both views ; but whichever 

 theory as to the seat of origin is accepted, there is no doubt 

 but that the disease is a chronic arthritis resulting in the pro- 

 duction of an exostosis, as it extends outwardly to the bone and periosteum. 

 Dollar applies the name periarticular ringbone to exostoses which occur 

 either at or in the immediate vicinity of the joint, when the articular car- 

 tilages are healthy. In this class he also includes exostoses which occur 

 at the seat of attachment of the synovial capsule, and states that false ring- 

 bone and periarticular ringbone are synonymous. Whether the con- 

 dition commences as a chondritis or synovitis, the joint is affected, and 

 the exostosis which forms has a tendency to surround the joint, thus con- 

 forming most accurately, as is generally accepted, to the name employed, 

 ring-bone. There is little doubt but that matters would be simplified in 

 dealing with this subject, and fewer litigatory conliicts would result, if 

 those exostoses which did not immediately affect the joint were excluded, 

 and considered in the same category as exostoses in the neighbourhood of, 

 but not directly affecting the action of, other joints. 



For our purpose we will therefore only treat as ringbones those 

 enlargements which affect the joint and are the result of chronic chon- 

 dritis or synovitis. 



As regards the exciting cause of the affection, there is but little doubt 

 that it is most frequently due, as Macqueen maintains, to concussion 

 aggravated by heavy work. Uneven distribution of the concussion also 

 over the articular surfaces cannot fail to have an injurious effect upon 

 the articular cartilage. 



