The Lameness Exam: What to Expect After You’ve Called the Vet

 
Among the many things that a horse owner dreads is going out to the barn and seeing your horse not moving right. It can be as simple as an occasional irregular stride on the lunge line or as dramatic as head-bobbing, hip-hiking lameness (or worse), but in either case, the next step is contacting the veterinarian and scheduling a lameness exam. Although there are some typical components to nearly every lameness exam—such as use of hoof testers and flexion tests--there is no one, standard “lameness exam” because every horse and every situation is different. For example, the tools and tests used for a horse who has taken some uneven steps competing at the highest levels of his sport may be very different from the way a vet approaches the diagnosis of a young horse that comes in from the pasture limping.
 

Initial Examination

Surprisingly, the first thing a vet will do when called out to examine a horse for lameness does not involve palpating the limbs or watching the horse jog — it’s gather a history. This means asking the owner, and possibly trainer, questions about the problem and encouraging them to describe what they are seeing and feeling, including when it first started, how it has changed and if any treatment has already been given.
 
Once the vet has these basic facts, the actual lameness exam itself can begin. Step one is a visual inspection at rest, before the horse is even asked to move. Here the vet is assessing conformation, balance and symmetry left to right as well as back to front, plus the horse’s overall posture and comfort level.
 
The next step is palpation, or feeling the various body parts by hand. Don’t be surprised if the vet palpates the normal limb first then moves to the abnormal limb. This is because it is helpful to be able to compare one leg to the other and to know what it is supposed to feel like for that particular horse before trying to decide if the way a specific structure looks or feels is not normal. Digital pulses (the intensity of the heart rate in the blood vessels of the lower limbs) may also be assessed. At this point, the vet may apply hoof testers to the feet, to determine if there’s any pain or discomfort when certain areas of the hoof are squeezed or pressed on. Armed with this preliminary data, it may now be time to observe the horse on the move.
 
Some veterinarians prefer to have the horse jog in-hand while others prefer to see the horse jog at the end of a lunge line. After watching the horse in motion, perhaps on both straight lines and circles, and on both hard and soft ground, the vet may wish to perform flexion texts.
 
In this procedure, additional stress is placed on specific joints such as the knee, fetlock (ankle), stifle, and hock by holding one leg off the ground in a bent position for a minute or two then putting it down and immediately trotting the horse off. Flexion tests are helpful to localize soundness issues by temporarily accentuating pain. So a horse that was a Grade 1 on the right front at first might demonstrate a Grade 2 or 3 lameness after the knee is flexed, indicating that may be where the problem is (see sidebar for more information on grading a lameness).
 

Additional Diagnostic Tests

Depending on the results so far, the vet may decide it is time to numb a limb, usually beginning at the bottom with the hoof and working up the leg. “Nerve blocks” are performed by injecting topical anesthetic agents just under the skin and over the top of nerves. Within a few minutes, structures served by these nerves become temporarily deadened and if pain was originating from that particular area of the leg, the horse may now jog out sound. However, if that area was NOT the source of the lameness, then the horse will jog the same as before and another area may then be blocked against pain. Entire joints can be numbed with a “joint block” in which the anesthetic agent is sterilely injected into the joint itself and, after waiting for the agent to take effect, the horse is jogged to see if there is any difference in his way of going.
 
The next service the vet may offer is imaging. Today’s veterinarians have a wide array of visualization tools at their disposal to aid in the diagnosis of lameness but these modalities do not take the place of a thorough lameness exam, they are complementary to it. Once a lameness has been localized to a specific area, the best tool for the job will be selected, such as radiographs (X-rays) for bones and joints or ultrasound for soft tissues like tendons and ligaments. Advanced imaging choices include scintigraphy (nuclear scan), MRI and/or CT scans. Sometimes images of specific structures can be used to rule in a cause for lameness—such as an OCD cyst in the stifle or a core lesion in the suspensory—and sometimes images can be used to rule out a cause for lameness—such as properly aligned fibers in the superficial digital flexor tendon or pristine articular cartilage surfaces in the hock joint.
 
From a horse that feels uneven in the reins or won’t pick up a certain canter lead to a non-weight bearing lameness (an emergency!), your vet is your best resource to get to the bottom of the issue quickly so that appropriate treatment can be started right away and you can get back to enjoying your horse!
 

Lameness Grading System 

A lameness grading system has been developed by the American Association of Equine Practitioners (AAEP) to standardize the degree of a horse’s unsoundness:
0: Lameness not perceptible under any circumstances.
1: Lameness is difficult to observe and is not consistently apparent, regardless of circumstances (e.g. under saddle, circling, inclines, hard surface, etc.).
2: Lameness is difficult to observe at a walk or when trotting in a straight line but consistently apparent under certain circumstances (e.g. weight-carrying, circling, inclines, hard surface, etc.).
3: Lameness is consistently observable at a trot under all circumstances.
4: Lameness is obvious at a walk.
5: Lameness produces minimal weight bearing in motion and/or at rest or a complete inability to move.
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