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G O O D R E ADS

Purely non weight-bearing lameness is generated by

limb. For an example, let’s say that your horse sinks into the RF

something that serves to actively move the limb forward,

limb, telling us that the LF limb is lame:

but does not bear an appreciable amount of the horse’s

• In the case of weight-bearing lameness, it will appear as

weight. In general, structures residing above the level of the

though your horse will step into a hole

horse’s carpus (forelimb) or tarsus (hind limb) most often fit

with RF limb. This action represents a

this description. If you guess that a horse displaying purely

transfer in weight from the lame (LF)

non weight-bearing lameness has a problem in the foot, you

limb to the comfortable (RF) limb. The

will be wrong every time. (See figure 4)

deeper the hole, the more severe the

Anatomy that serves to both bear the horse’s weight and

weight-bearing lameness.

move the limb forward will generate combination deficits when affected. Generally speaking, structures residing above

• In the case of non-weight-bearing lameness, it will appear as

the level of the fetlock and below the level of the carpus

though your horse is dragging a weight

(forelimb) or tarsus (hind limb) most often fit this description.

with the LF limb. This action represents

If the duties of load bearing and limb protraction are equally

an increase in effort needed to advance

distributed, then the resulting lameness will have equal

the lame (LF) limb forward. The heavier

weight-bearing and non weight-bearing components. If

the weight, the more severe the non-

the affected structure bears a lot of weight but moves very

weight-bearing lameness.

little, the horse will display a combination lameness with a predominant weight-bearing component. So in essence, you can learn the function of the tissue

• By reason, a combination lameness will look like your horse is stepping into a hole with the RF limb while concurrently

causing the lameness simply by determining the nature

dragging a weight with the LF limb.

of the lameness. In similar fashion, you can predict what a

When we see this, we know that the

lameness will look like if generated by a specific part of the

insulting tissue bears the horse’s weight

horse’s anatomy. We can predict that a problem in the foot

and moves the limb forward, and it’s

will generate a weight-bearing lameness because it obviously

most likely to reside somewhere along

bears the horse’s weight, but doesn’t distort appreciably when

the mid-limb.

the horse moves the limb forward. By contrast, the horse’s biceps tendon (located along the front of the shoulder)

This concept may seem fairly simple, but I use this technique

doesn’t serve to bear any significant amount of weight.

in my regular practice of veterinary medicine. For instance, many

It moves dramatically to help the horse advance the limb

MRI reports that I read contain up to a half dozen different

forward, however. Accordingly, we can predict that bicipital

diagnoses listed by the attending radiologist. This means that

problems will always generate a purely non weight-bearing

there are about six structural abnormalities visible on the images.

lameness. (See figure 5).

Are all of these things causing the horse’s lameness? Definitely

This sounds good, but how do you tell the difference

not! So which problem do I treat? My ability to determine the

between horses exhibiting weight-bearing, non-weight-

nature of the horse’s lameness through clinical examination (or

bearing, and combination lamenesses? It’s actually very easy.

video review) tells me what the structure causing the lameness

Like we said before, the horse will sink into the comfortable

essentially “does for a living.” Accordingly, I can effectively

limb, telling us that the opposing limb is the uncomfortable

rule-out the radiographic diagnoses that implicate tissues that

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EQ AM Spring 2019  

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