Page 999 - Adams and Stashak's Lameness in Horses, 7th Edition

Occupational‐Related Lameness Conditions 965

LAMENESS EXAM
VetBooks.ir plagues nearly every Standardbred racehorse at some
Lameness is a leading cause of poor performance that
point during its career. Compared with many other dis­
ciplines, a high percentage of hindlimb lameness prob­
lems are encountered as a result of the Standardbreds’
symmetrical gaits and having to pull a draft load.
History taking should include age, stage of training,
and whether the horse is a trotter or pacer. Owners
should be asked if the horse is lame or simply not per­
forming well. Young Standardbreds experience a subset
of problems not commonly seen in the mature horse,
and examination of unproven 2‐ and 3‐year‐olds with
poor performance must be sufficient to rule out the car­
diovascular or respiratory systems as the cause.
Lame horses should be examined for signs of local­
ized inflammation (heat, swelling, or pain), and the
trainer asked about the duration of the problem. It is
important to ask about the size of the track that the
horse races on and whether lameness is worse in turns
or on the straightaway. Most harness races are a mile
long, but track lengths do vary. On smaller tracks, horses
must negotiate more turns and the turn diameter is less.
Lameness from the medial side of the limb is more evi­
dent in the turns, whereas lameness from foot pain,
splints, and curbs worsens with distance and is likely
more obvious at the end of a race. A change of racing
venue may prove successful for horses with chronic
lameness issues. For example, a trotter with stifle arthri­ Figure 9.16. This 2‐year‐old Standardbred pacer demonstrates
tis may perform better on a 1‐mile track where it only being on a shaft. The colt’s hindquarters are positioned closer to the
has to negotiate two turns. right shaft of the sulky. This colt is also on the left line, and its head
It should be noted whether the horse “breaks is turned to the left as the driver pulls harder on the rein in an
stride” (gallops instead of maintaining the trot or attempt to keep the horse straight. This combination of findings
suggests a left hindlimb lameness.
pace), which is a serious fault for the harness horse.
Hock pain causes horses to get uneven coming into or
out of the turns, but they usually maintain the gait, a race because they try to avoid loading the inside of the
whereas fetlock and stifle lameness often cause horses limb (Figure 9.16).
to break stride in the turns. Horses can break for Interference may mimic lameness if horses alter their
many reasons other than lameness, including excite­ stride to avoid hitting another limb, and it can result in
ment, immaturity, and incoordination, and interfer­ bruising and lacerations that do cause lameness.
ence is a major cause of breaking. In this case, shoeing Alterations in gait can also cause horses to overload
or tack changes may correct the problem. The “bute other limbs and develop compensatory lameness, which
test” can be helpful to differentiate lameness from is so common in the Standardbred that veterinarians
interference: a horse is prescribed a modest course of must always consider the possibility that new problems
phenylbutazone and then reexamined. It is believed have arisen. Both primary and secondary lameness issues
that lameness improves with the nonsteroidal anti‐ must be addressed to achieve soundness. Trotters tend to
inflammatory medication while interference remains develop diagonal lameness problems, whereas pacers
unchanged. Neurologic disease also must be consid­ may develop ipsilateral or contralateral issues. Tack
ered in any horse with unresolved gait abnormalities. changes such as the addition of hobbles, boots, or a head
Several terms unique to Standardbred racing provide pole often indicate high‐speed lameness and should be
information about a horse’s performance. “Bearing in” assessed.
or “bearing out” means a horse drifts toward the infield Finally, the clinician must know the horse’s history,
or the outside rail, respectively. Drivers may comment including racing performance, prior lameness, treat­
that a horse is “on a line,” indicating that they must pull ments, and response to those treatments. Detailed record
harder on one rein to keep the horse from bearing in or keeping is imperative, since many owners and trainers
out. Horses drift away from a source of pain, so a horse prefer jumping straight to treatment rather than pursu­
on the right line is likely to have right front lameness. ing extensive diagnostic tests. Without a complete diag­
Alternatively, for rear limb problems, the hindquarters nosis, response to treatment becomes the barometer of
may move closer to one shaft of the sulky, and the horse clinical accuracy. Standardbred trainers may try to treat
is then described as being “on a shaft” (Figure 9.16). problems on their own, resulting in conflicting clinical
There are exceptions so this information must only be findings. It is not uncommon to be presented with a
used as a guide. Horses with right front medial heel horse that has “had all his joints done” (meaning intra‐
pain, for instance, are commonly on the left line during articular injections) but is still not performing well.