Page 62 - May 2018 Speedhorse

Careful observation, thorough examination, and persistence are necessary in working up many lameness problems.
Dr. sarah H. sampson, Dvm, PhD, DaCvs, DaCvsmR
Equine Initiative website: tamuequine.com
CVM website: vetmed.tamu.edu
The lameness of a horse is one of the most com- mon problems that an equine practitioner is called upon to treat. Veterinarians use a system- atic approach during the course of an exam so that
it is more likely that an accurate diagnosis is made. Careful observation, thorough examination, and persistence are necessary in working up many lame- ness problems. Some problems can be diagnosed in a few minutes from the history and clinical examina- tion; others require diagnostic local anesthesia (nerve blocks) and several hours of evaluation to determine the source of the lameness.
History, signalment, and Use
Examination of the horse for lameness begins with a thorough and accurate history. The history can be
as important as the clinical signs in leading one to a diagnosis, and this is especially true for difficult or ob- scure lameness problems. The signalment (age, breed, sex) of a horse is also very important, as many causes of lameness are more common in a certain age of horse or a certain breed of horse. For example, a young horse with joint effusion (extra fluid in a joint) is likely to have an osteochondrosis (OC) lesion, whereas an aged horse with joint effusion is more likely to have osteoar- thritis or a traumatic joint injury.
The use or discipline of a horse is a vital part of the history, as many lamenesses result from the type of ath- letic work that the horse performs. A racehorse is going to have specific common lameness issues related to the work they do, compared to lameness issues common to a dressage horse or a rope horse, for example.
Characterizing the lameness is also important. How long has the lameness been present? How severe has it been? Is the lameness intermittent or constant? Has the lameness been improving or getting worse? Does the lameness improve or become worse with exercise? Does the horse improve on phenylbutazone? Has the horse been rested in a stall, continued in work, or turned
out? When did the horse last train or race? Was the horse non-weight bearing on the leg at any time? Has there been heat or swelling in the leg? These types of questions are necessary to obtain a mental picture of the horse’s lameness prior to the examination. For example, a horse that came up acutely lame during a barrel race may be more likely to have a bone bruise or a tendon injury. Whereas, a horse that has been off and on mildly lame for a few months and improves as the horse is warmed up may be more likely to have osteoarthritis in a joint that is slowly progressing.
recognition of lameness
The first step in any lameness examination is to correctly identify the lame limb(s). This requires good powers of observation and experience watching horses move. Normal horses move with balance and bilateral symmetry; they land with equal concussion and move with equal stride length on both the fore and the
rear limbs when they are compared side-to-side at a trot. Variation in the normal gait occurs when horses experience pain during movement, have neurologic deficits that affect proprioception and strength, or have a mechanical problem that limits limb use.
Although there are a few gait abnormalities in horses that are mechanical (do not have pain associ- ated with them), most changes in gait are a response to pain. The horse feels pain when it flexes the leg or when weight is transferred across the leg. With most orthopedic problems, pain occurs both during flexion and on concussion when the foot strikes the ground. The horse alters his gait to minimize pain and exhib- its gait changes that we recognize as lameness.
Because the horse experiences pain every time the limb is used, lameness gaits are typically consistent and repeated every stride as the horse moves. There- fore, lameness gaits are typically regularly irregular; the horse lands with decreased concussion or shortens his stride the same amount with every step. Mechani- cal gait abnormalities also tend to be consistent and repeated with every stride, although there is more variation with mechanical gait problems than with lameness.
Neurologic gait deficits, on the other hand, are very inconsistent and these horses tend to be ir- regularly irregular. Their foot flight, length of stride, and concussion may all vary with each stride. The concept of irregularly irregular is an important one. Neurologic problems are common in horses and the resulting gait abnormalities can be easily confused with lameness. Some horses have both neurologic gait deficits and lameness, making it even more difficult for the examiner to identify the problem. Thorough and careful observation is essential to sorting out the cause of the horse’s abnormal gait.
Lameness examination should always include evaluating the horse at both a walk and a trot, and sometimes at the lope/canter, and/or under saddle, and/or performing in their respective discipline. Most lameness problems are easier to see when the horse is worked at the trot because it is a 2-beat symmetrical gait that makes changes in concussion or stride length
Lameness evaLuaTion
By Sarah N. Sampson, DVM, PhD, DACVS, DACVSMR, Assistant Professor, Equine Sports Medicine & Imaging, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University • photos courtesy Texas A&M
60 SPEEDHORSE, May 2018
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