Page 1198 - Adams and Stashak's Lameness in Horses, 7th Edition

1164 Chapter 12

cantering, or simultaneous hindlimb push off at the can­ Saddle slip where the saddle consistently slips to one
ter (“bunny hopping”). Assessment of gait change after side of the horse back has been blamed on ill‐fitting
VetBooks.ir saddle and bridle and their suitability can be assessed. ness influences the presence of saddle slip, with most
saddles; however, current research indicates that lame­
implementation of tack can also be helpful. Fit of the
saddles slipped to the side of the lame hindlimb. In
Systematic application of one or more pieces of tack,
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side reins at various degrees of tension, or weighted sur­ these horses, comprehensive evaluation including keen
cingle may induce axial skeletal pain and/or exacerbate observation by the attending veterinary is paramount
lameness. to distinguish inciting causes from their resultant gait
Since many poor performance abnormalities are only abnormality.
apparent or exacerbated with a rider, the next step is the
ridden evaluation. This is particularly true in sport
horses when the abnormalities occur only during spe­ DIAGNOSTICS
cific movements, sport‐specific gaits, and/or changes of
pace such as canter‐to‐trot transitions. In these horses, Diagnostic analgesia can help determine if the horse’s
ridden exercise is critical. Traditionally, gait abnormali­ poor performance is due to musculoskeletal pain vs.
ties noted with the application of a saddle and rider behavioral, training, or other problems. In addition,
have been attributed to back pain. Affected horse may nerve and joint blocks can elucidate the authentic site of
exhibit shortened length of stride, lack of hindlimb underlying pain. Neck, back, and pelvic abnormalities
impulsion, reluctance to work, and/or a stiff back. are commonly incriminated by their riders; however, the
However, these clinical signs are not pathognomonic for presenting clinical signs in these horses such as body
back pain. Lame horses, especially those with bilateral stiffness, resistance to rider aids, and unwillingness to
hindlimb lameness, also exhibit the same abnormal gait bend are also exhibited in horses with limb lameness. In
characteristics. Lame horses adapt their gaits by decreas­ these horses, resolution of the abnormal gait following
ing extension of the thoracolumbar‐sacral region. This palmar digital analgesia is definitive evidence that the
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resultant trunk stiffness is often perceived as back pain clinical signs are due to foot pain and not due to axial
by the rider even though the underlying pain and skeleton pain. In horses with bilateral symmetrical lame­
decreased back flexibility are due to limb lameness. ness, simultaneous blocking of both limbs may be diag­
Nervous or anxious horses may also exhibit short nostic. For example, in Thoroughbred racehorse with
choppy gaits and stiffen or tense their backs until they short choppy hindlimb gait, blocking the distal plantar
are more comfortable with their surroundings. metatarsal nerves in both hindlimbs may be indicative
The addition of a rider’s weight increases the load of plantar osteochondral disease of the distal third met­
applied to the horse’s limbs, which many explain why atarsus. Alternatively, response to joint therapy may be
many horses with subtle lameness, especially hindlimb used for diagnosis. However, not all horses with painful
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lameness, are only visibly apparent when ridden. joints will respond favorably to intra‐articular medica­
Complaints of horses being more comfortable when tions, and limited or no improvement in clinical signs
trotting in one direction or posting on one diagonal may does not necessarily eliminate those sites as the source of
be associated with unilateral hindlimb lameness. Peak problem.
forces are higher on the sitting trot diagonal compared Comprehensive nuclear scintigraphic evaluation can
with the rising trot diagonal, and hindlimb lameness is be beneficial in the poor performer. It is particularly use­
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often worse when the rider sits on the diagonal of the ful in the racehorse with intermittent lameness, appeared
lame leg. In addition to uneven load stresses on the to be “sore all over,” and those with mild bilateral gait
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limbs, rising trot also creates asymmetrical stresses on abnormalities. Common abnormalities include distal
the back. Increased lameness and/or back stiffness is fre­ palmar/plantar fetlock pathology, bilateral upper limb
quently more obvious during sitting trot vs. trotting in stress fractures, and pelvic fractures. Scintigraphic imag­
the jumping position. Horses with back pain or bilateral ing in riding horses may also be a valuable diagnostic
hindlimb lameness may be resistant to collected move­ aid. Axial skeletal disease, sacroiliac abnormalities, and
ments or other maneuvers that require the rider to sit rib lesions can be identified with this modality. Albeit
deeply in the saddle. frustrating, a “negative” bone scan does not necessarily
Based on what the owner feels when riding, they indicate the horse does not have a musculoskeletal prob­
often formulate assumptions regarding the underlying lem. Horses with stifle synovitis and soft tissue injuries
cause of the horse’s clinical signs. However, rider pre­ such as proximal suspensory desmitis frequently do not
conceptions should be interpreted cautiously since they have associated areas of increased radiopharmaceutical
may be incorrect. For example, difficulty bending cor­ uptake.
rectly in a circle or the horse being heavy in the bridle is There are many other reasons for a horse to experience
often perceived as neck pain by the rider. Although decline in performance, and additional investigations
horses with cervical pain can exhibit these abnormali­ may be necessary. Subtle neurological problems can
ties, more often these gait abnormalities are due to fore­ have a dramatic effect on gait. For horses that trip or
limb lameness. In response to pain, horses with mild exhibit disunited gaits or incoordination, a complete
forelimb lameness will shift their head and neck to one neurological evaluation is indicated including cervical
side prior to overt limping and obvious head/neck nod. imaging and cerebrospinal fluid analysis. Testing for
For riders, this uneven head and neck position results in muscle conditions such as polysaccharide storage myo­
increased rein pressure or heaviness in one hand. Horses pathy or exertional rhabdomyolysis may also be benefi­
with mild bilateral symmetrical forelimb lameness may cial. Abnormalities of the cardiac and respiratory
feel like they are “heavy on the forehand” to the rider. systems are also common in poor performers. Previously