SESAMOID LAMENESS. 875 



metacarpus. This probably explains Mascher's statement that 

 where the toes are turned in, the outer sesamoid is affected, and 

 vice versa, for such defective conformation must necessarily lead to 

 unequal pressure on the sesamoid bones. Heavy bodies and weak 

 fetlocks predispose to the disease, which is commonest in " weedy " 

 hacks and hunters, and in draught-horses with long, sloping 

 pasterns, and occurs principally 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 sheath being often simul- 

 taneously affected at a point close to the fetlock-joint. 



Symptoms. In the chronic form, lameness is a constant 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. 



Manipulation of the back of the fetlock gives pain. After some 

 time the sesamoid bones become enlarged. If the anterior surface 

 of the sesamoids is involved, the enlargement is close to the meta- 

 carpus, i.e., at the side of the joint ; in disease of the posterior surf ace 

 it is further back on the volar aspect of the joint. After a further 

 variable period the flexor tendons become swollen in the neighbour- 

 hood 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 " at the fetlock-joint, from 

 thickening of the tendons. In one case Brauell found the sesamoids, 

 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 neurectomy or slaughter. 

 Lameness becomes worse after severe exertion, but tends to disappear 

 with rest. Complete recovery is, however, very rare once the disease 

 has become well developed. 



