SESAMOID LAMENESS. 
627 
may produce this disease, and therefore both Brauell and Mascher regard 
long, weak fetlocks as the chief predisposing factor. This formation not 
only throws a greater strain on the tendons, but increases the pressure 
on the sesamoid bones, on account of the more oblique angle which the 
tendons make with the metacarpus (compare with section on “ Navicular 
Disease”). This probably explains Masclier’s statement that where the 
toes are turned in, the outer sesamoid is affected, and vice versa, for 
such defect of conformation must necessarily lead to unequal pressure 
on the sesamoid bones. Heavy bodies and weak fetlocks predispose to 
the disease, which is therefore commonest in hacks and heavy draught- 
horses, and occurs without exception in the fore limbs. Other causes 
are jumping, especially from a height, and suddenly reining up. In 
such cases, partial rupture of the flexor tendons probably occurs and 
starts the disease; Siedamgrotzky reports an observation of the kind. 
The disease may then set in with acute inflammation, but as a rule it 
develops slowly, the flexor sheaths being often simultaneously affected 
at a point close above the fetlock-joint. 
Symptoms. In the chronic forms, lameness is the most apparent 
symptom. As in all affections of the flexors, pain is greatest when 
weight is placed on the limb, the phalanges are flexed and the limb is 
rested. Volar flexion is in most cases well marked. Lameness is most 
distinct during the first few steps, but may disappear with exercise; it 
is decreased by long rest, increased by exertion, is more marked on 
rough, hard ground than on sand or grass, and is sometimes so slight 
as only to be detected by carefully watching the animal whilst trotting, 
though in severe cases it is apparent at a walk. 
Palpation of the hack of the fetlock gives pain. After some time a 
bony swelling appears, corresponding in position to the sesamoid bones. 
If the anterior surface of the sesamoids is involved, the swelling is close 
to the metacarpus, i.e., at the side of the joint; in disease of the 
posterior surface, it is further back on the volar aspect of the joint. 
After a further variable period, the flexor tendons become swollen in 
the neighbourhood of the sesamoid bones, though such swelling may 
occasionally appear before the other symptoms. The acute form is 
distinguished by local heat, &c., which is absent in chronic cases. 
During the later stages there is “ knuckling over ” at the fetlock-joint, 
from shortening of the tendons. In one case Brauell found the sesa¬ 
moids, in consequence of the marked volar flexion, thrust upwards 
beyond the articular surface of the metacarpus, and adherent in their 
new position. Movement of the fetlock-joint is often distinctly limited. 
Crepitation can rarely be detected. 
The course is chronic, inflammation seldom subsiding, but continuing 
for long periods, and necessitating slaughter. Lameness becomes worse 
s s 2 
