Page 102 - Adams and Stashak's Lameness in Horses, 7th Edition

68 Chapter 2

2. Swinging limb lameness: Evident when the limb is in
motion. A variety of pathologic changes may be the
VetBooks.ir 3. Mixed lameness: Evident both when the limb is mov­
cause, and the majority of these problems are thought
to involve the upper limbs or axial skeleton.
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ing (swing phase) and when it is supporting weight
(stance phase). Mixed lameness can involve any com­
bination of structures affected in swinging or sup­
porting limb lameness.
4. Primary or baseline lameness: Most obvious lame­
ness or gait abnormality that is observed before flex­
ion or manipulative tests. 7,33 This can be complicated
by lameness in multiple limbs, but in most cases the
lameness that is the worst is considered the primary
lameness. Evaluation of the primary lameness should
be performed initially before scrutinizing comple­
Figure 2.1. Chronic hindlimb lameness that has resulted in a mentary lameness problems.
wide flat foot on the sound left hindlimb and a narrow, upright hoof 5. Compensatory or complementary lameness: Pain in a
on the lame right hindlimb. limb can cause uneven distribution of weight on
another limb or limbs, which can produce lameness
measure for the vertical ground reaction force and is in a previously sound limb. It is common to have
reduced in the lame limb at the stance phase proportion­ complementary lameness produced in a forelimb as a
ally to the degree of lameness. 12,32,39 In addition, in horses result of lameness in the opposite forelimb. Also, a
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with chronic lameness, the limb with the flatter hoof lameness in a hindlimb can mimic a forelimb lame­
exhibits higher vertical loads because it is the non‐lame ness on the ipsilateral side (right hind and right fore).
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limb (Figure 2.1). Detecting these compensatory move­ Quantitative lameness evaluations suggest that an
ments is an integral part of diagnosing lameness in the apparent lameness in the forelimb and hindlimb on
horse. The most consistent compensatory movements the same side often suggests a primary hindlimb
that are observed are the vertical displacement and accel­ lameness and a false compensatory forelimb lame­
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eration of the head in forelimb lameness and of the ness. Additionally, lameness in one hindlimb may
sacrum and tuber coxae in hindlimb lameness. 11,25,39 contribute to lameness in the opposite hind.
Although overlap of these movements can occur (head Even minor changes in weight‐bearing can produce
movement with hindlimb lameness and pelvic movement complementary lameness at high speeds, especially over
with forelimb lameness), they tend to occur primarily in long distances. The feet, suspensory ligament, sesamoid
moderate to severe lameness. In addition, more subtle bones, hocks, and flexor tendons seem to be affected
lameness causes fewer compensatory changes, making most commonly. Complementary lameness in the same
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lameness diagnosis more difficult, and problems within limb usually results when excess stress occurs to an oth­
the axial skeleton (back) may also alter the movement of erwise healthy structure in an attempt to protect a pain­
the limbs. 19,39 Although some of these gait changes may ful region in that limb. For example, a horse with
be difficult to appreciate during visual examination of a navicular syndrome often lands toe first, potentially
lame horse, it should be remembered that the primary contributing to toe bruising and/or osteitis.
adaptive strategy of the horse is to redistribute load to By observing the gait from a distance, one can usually
compensate for pain in a limb without causing an over­ determine whether the lameness is supporting limb,
load situation in other limbs. 39
swinging limb, or mixed. Some conditions that cause
supporting limb lameness may cause the horse to alter
CLASSIFICATION OF LAMENESS the movement of the limb to protect the foot when it
lands. This can be mistaken for swinging limb lameness.
There are a variety of ways to classify lameness in the Because of this and other adaptive strategies that occur
horse. In most cases there is a primary or baseline lame­ in lame horses, some clinicians feel that mixed lameness
ness that contributes to the most obvious gait abnor­ occurs most commonly in horses. 33
malities. Compensatory, secondary, or complementary
lameness results from overloading of the other limbs as
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a result of the primary lameness. Lameness may also Character of the Stride
be classified according to when it occurs (or is best The character of the stride of a limb is important to
observed) within the stride. The different classifications the diagnosis of lameness. When observing the stride,
of lameness are defined below:
the following characteristics should be observed:
1. Supporting limb lameness: Apparent when the foot The phases of the stride: The stride consists of a cra­
first contacts the ground or when the limb is support­ nial phase and a caudal phase. The cranial phase of the
ing weight (stance phase). Injury to bones, joints, soft stride is in front of the footprint of the opposite limb,
tissue support structures (e.g. ligaments and flexor and the caudal phase is behind it (Figure 2.2). With lame­
tendons), and the foot are considered causes of this ness, the cranial or caudal phases may be shortened. If
type of lameness. This is by far the most common the cranial phase is shortened, there may be a compensa­
type of lameness identified in the horse. tory lengthening of the caudal phase, and vice versa.