Page 169 - Adams and Stashak's Lameness in Horses, 7th Edition

Examination for Lameness 135

Although amount of limb abduction or adduction during There are numerous other subjective observations
the swing phase of the limb has been thought to be indica­ thought to indicate lameness in the horse, including amount
VetBooks.ir objectively studied. Placement of the hoof during weight‐ ment, sequence and timing of foot fall cadence, being “on
of head flexion when ridden, overall straightness of move­
tive of certain lameness conditions, this has not been
the bit,” amount of “engagement” of the hindlimbs, “ease”
bearing either directly under (less lame limb) or abaxial
(more lame limb) is, ostensibly, a sensitive indicator of of transition from one gait to another, overall willingness to
lameness. However, this author has measured this in many move, and many others. When lameness is difficult to
horses with induced lameness and found this to be incon­ detect because asymmetric vertical movement of the head
sistent and contradictory. and pelvis is less than what can be seen by the naked eye,
the veterinarian is forced perhaps to then attempt to
observe many different things. In general, limb movement,
HOOF TRAJECTORY ASSOCIATED WITH LAMENESS pelvic rotation, and other highly subjective observations
may be used to help confirm the existence and extent of
The length and shape of forelimb and hindlimb hoof lameness and in some cases may even hint at the location
trajectory during the swing phase of the stride are com­ of abnormality within a lame limb, but they should not
monly perceived to be associated with lameness. contradict vertical head and pelvic parameters that are
However, objective measurements of these changes have directly related to altered vertical ground reaction forces,
not been confirmed, and in a few cases have contra­ and if they do, they should be considered idiosyncratic and
dicted, these perceptions. Forelimb protraction, the cra­ not indicative of abnormality. Some clinicians have claimed
nial phase of the hoof flight arc, will either decrease or even that lameness can be observed by detecting expres­
increase with lameness, depending upon type of lame­ sions on the horse’s face during riding or lunging, an equine
ness. For example, in the foot, heel lameness (e.g. “pain face.” However “painful” facial expressions may
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navicular disease) generally decreases, but toe (e.g. lami­ signify discomfort in any body system or because of a vari­
nitis) lameness generally increases forelimb retraction. ety of causes including those that cause lameness.
However, hindlimb protraction is usually decreased in
most cases of hindlimb lameness. Unilateral decreased
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hindlimb protraction is easy to recognize in the lame LAMENESS EVALUATION DURING
limb at the trot by visualizing the distance between the IPSILATERAL GAITS
affected hindlimb at full protraction and the ipsilateral The vertical movement trajectories of the head and
forelimb at full retraction (Figure 2.126). This distance pelvis during the rack and pace are identical in concept
is longer on the lame side. However, a simultaneous but smaller in amplitude compared to that found at the
increase in retraction of the forelimb, which occurs in trot. The body still moves down during the first half and
some forelimb lameness conditions, will interfere with up during the second half of stance. Therefore the same
the proper interpretation of this sign. 12 principles of altered movement with lameness can be

Figure 2.126. Hindlimb protraction is easily seen when viewing in most hindlimb lameness; thus, the space between the retracted
from the side of the horse. The hoof of the retracted ipsilateral forelimb and protracted hindlimb is greater (arrows) on the lame
forelimb acts as a point of reference. Hindlimb protraction is reduced hindlimb side.