608 
RING-BONE. 
Dieckerhoff says that ring-bone results from inflammation of a small 
bursa mucosa lying between the branches of the perforatus tendon and 
the postero-lateral ligaments of the navicular bone. It is quite true 
that swelling of this bursa may be mistaken for ring-bone; but it 
seems very doubtful whether disease of the joint or lameness is ever 
caused by it. 
Symptoms. The common basis of these conditions is chronic 
enlargement around the coronet-joint, which is sometimes so slight as 
only to be detected by careful examination and comparison of the two 
feet. In such cases, of course, the limbs must be placed as nearly as 
possible in similar positions. Exostoses on the lateral surfaces of the 
joint are best seen from the front; those on the anterior surface from 
the side, and from the height of the affected foot. Diagnosis is also 
assisted by palpation and comparison of the two joints. 
In articular ring-bone the exostosis extends from either side over 
the anterior surface of the joint, and appears more or less circular, from 
which circumstance it has received its name. The posterior surface is 
covered by the ligaments and flexor tendons, and therefore cannot well 
be examined. The exostosis sometimes arises chiefly from the suf- 
fraginis, and is then rather higher placed, sometimes from the coronet, 
when it is found just above the hoof. A high and low form of ring-bone 
have therefore been distinguished. The swelling is hard, painless on 
pressure, and the skin covering it is movable. 
The periarticular form is similar in appearance, except that the 
enlargement is usually confined to the lateral surfaces of the suffraginis 
and coronet bones, and the anterior surface is usually normal. As in 
the former case, the swelling may appear higher or lower, and in general 
what has been said above also applies to this form. 
Lameness is an almost constant feature of both these forms of ring¬ 
bone. It occurs principally when weight is placed on the limb, and is 
sometimes considerable, sometimes only slight. Lameness is absent in 
rhachitic ring-bone, and usually in the traumatic form. After a long 
rest it may partly disappear, and in spirited animals slight lameness is 
often lost during movement. When the condition has become chronic, 
the muscles of the limb atrophy, wasting being proportioned to the 
chronicity and severity of the lameness. As a rule the latter phase of 
the stride is considerably shortened, and the phalanges show volar 
flexion, i.e., the fetlock is upright. In the periarticular form, lameness is 
best seen when the animal turns in short circles towards the diseased 
side. It is a consequence of inflammation of the articular surfaces or 
of ligaments, though at times it results from mechanical obstruction to 
movement in the coronary joint, due either to the formation of exostoses 
or to contraction of ligaments, and adhesions between the articular 
