Extension of the hock in upward
luxation of the patella, permits of flexion of the phalanges. In upward
luxation, then, the leg is extended as if too long, but the phalanges
may be in a state of moderate flexion. If the foot rests on the ground
when the extremity is not flexed, it is almost impossible for the
subject to step backward. Because of immobilization of the stifle and
hock joints in upward luxation, the subject can walk only by hopping on
the sound leg and then the extremity is flexed, allowing the anterior
portion of the fetlock to drag on the ground.

In some cases practitioners are called to attend young animals that are
reported to be "stifled" (often in young mules that have made a rapid
growth) and upon arrival the only noticeable symptom of preexisting
luxation is the soiled condition of the anterior fetlock
region--evidence of its having been dragged. Such cases may be styled
momentary luxation, whether they are due to a weakened condition of the
patellar ligaments or spasmodic contraction of the crural muscles.

In upward luxation, reduction is effected by attempting further
extension of the stifle joint and at the same time the patella is pulled
outward, off the internal rim of the trochlea. This is attempted by
securing the subject in a standing position; the sound side is kept
against a wall if possible and a rope is tied to the extremity of the
affected leg. Traction is exerted upon the rope and at the same time
force is directed against the stifle joint to produce further extension
if possible, so that the straight patellar ligaments may relax
sufficiently to allow the patella to be dislodged from its position upon
the inner trochlear lip. Failing in this manner of procedure, the
affected animal is to be cast and anesthetized with chloroform. The
relaxation which attends surgical anesthesia will permit of reduction of
the dislocated bone and manipulations such as have just been outlined
may be employed.

Following reduction in the average case it is essential that the subject
be given vigorous exercise for a few minutes. Reduction having been
affected, the application of a vesicant over the whole patellar region
is customary.

In cases of habitual luxation, unless the ligaments are so lax that the
patella may be displaced laterally over the inner as well as the outer
trochler rims, division of the inner straight patellar ligament will
correct the condition. This desmotomy has been advocated b