CAUSES OF INFLAMMATION OF THE FLEXOR TENDONS. 
571 
which the tendons are placed. For a similar reason, horses with “ tied- 
in” knees are disposed to tendinitis, this formation being generally 
accompanied with small size of the fetlock. Further, everything which 
favours dorsal flexion of the joint increases risk of inflammation of the 
flexor tendons. Low heels and long toes are therefore apt to cause it. 
Long toes throw a powerful strain on the flexor tendons during the 
latter phase of movement, just before the limb is lifted from the 
ground. The kind of work required of the horse is also important. 
Thus race-horses and hunters, and horses required to trot at a sharp 
pace for long periods, are the most general sufferers. Animals with con¬ 
siderable powers of endurance suffer most. The greater the muscular 
development of the hind-quarters, the greater the shocks produced in the 
fore limbs by the violence with which the weight of the body is thrown 
forward on to them. Spirited animals suffer more than phlegmatic. 
For similar reasons, cart-horses show strain more frequently in the 
hind limbs. Those which work in two-wheeled carts and have oblique 
pasterns are specially liable to strain of the hind limbs, particularly when 
descending hills with heavy loads. 
Strains of flexor tendons are produced either by the body-weight 
suddenly falling on the front limbs when the horse is jumped or quickly 
pulled up (passive strains), or by continued violent action of the flexor 
muscles (active strains). In the first instance, the flexor perforatus is 
principally involved, its less length causing it to suffer first from forced 
dorsal flexion of the phalanx. The flexor perforans is less likely to be 
injured. The effective length must be reckoned as the distance between 
the lower insertion and the upper one, and in the perforans and perforatus 
tendons from the upper insertion of their so-called check ligaments. 
Inflammation of tendons produced by excessive muscular action 
(active sprains) have, with few exceptions, their seat in the flexor per¬ 
forans, because the muscular head of this tendon is by far the stronger, 
and its tendon is therefore exposed to the greater strain. But passive 
strains also occur, as shown by the frequence with which the check liga¬ 
ment, which extends to opposite the middle of the metacarpus, becomes 
diseased. With regard to strain of the check ligament, which is 
particularly common in cart-horses, the remarks made in the previous 
chapter re strain of the suspensory ligament in large measure apply. The 
conditions, however, are not precisely the same, because owing to their 
respective mechanical arrangements strains do not affect the suspensory 
and check ligaments in exactly the same way. Judging from their course 
and attachments, it would appear that while the suspensory ligament is 
always more or less in tension, the check ligament is frequently entirely 
relaxed, and that stress, when thrown on it, is liable to be of the nature 
of a sharp jerk. Such a jerk would follow any miscalculation of distance 
