748 
DISEASES OF THE HOCK. 
IX.—LUXATION OF THE FLEXOR PEDIS PERFORATUS 
TENDON. 
I he flexor pedis perforatus tendon, at the spot where it plays over the 
Point of the hock, is expanded into a kind of cap. A short but powerful 
prolongation of the tendon is inserted into the os calcis on either side, 
just in fiont of the point of insertion of the tendo Achillis, which 
prevents the tendon slipping off the tuberosity of the calcis bone. Some¬ 
times one of these ligaments is ruptured, allowing the tendon to glide 
off the calcis towards the opposite side, and to lie on the lateral surface 
of the hock. Gunther describes a case of dislocation towards the inner 
side ; others have seen it occur outwardly. The direction depends, of 
couise, on which attachment is ruptured. As the tendon passes over 
the hock from within outwards, one would expect that the external 
attachment would most frequently suffer, and that dislocation would be 
towards the inner side. On the inner side the tendon either remains 
fixed about half-way up the astragalus, or slips down as far as the 
articular prominence of that bone. 
Such luptures occur during heavy work, or follow external injuries 
like kicks, &c. 
Symptoms. Displacement is rarely followed by severe lameness ; the 
gait is insecure, weak, and rolling, and the animal appears to have lost 
full conti ol of the limb. Standing behind the horse, the tendon is seen 
to glide off the tuber calcanei every time the hock is extended, and often 
to return to its normal position when the joint is flexed. In other cases 
the tendon, though displaced, can easily be returned to its position on 
the point of the calcis; but almost immediately becomes again luxated. 
When the tendon and neighbouring parts are inflamed from kicks, &c., 
the swelling and pain produce a more marked lameness, otherwise 
movement is only mechanically interfered with. While the horse stands 
on the limb, the lower joints show dorsal flexion, consequent on relaxation 
of the flexor pedis perforatus, but the hock-joint is extended. 
Prognosis. Recovery is uncertain on account of the difficulty of fixing 
the hock for a sufficient length of time to allow the ends of the ruptured 
ligament to unite. Even though, by flexing the thigh, the tendon can 
be replaced, it tends to slip out of position the next time the thigh is 
extended or weight is placed on the limb. As a rule, little improvement 
can be expected, and only in cases where inflammation produces local 
pain does the lameness even diminish. 
As a rule, the animals can only do light walking-work, and are quite 
useless for riding or for heavy draught. 
Treatment is confined to checking the-local inflammation sometimes 
seen in recent cases. Drouet suggests suturing the tendon, and 
