Page 1051 - Adams and Stashak's Lameness in Horses, 7th Edition

Occupational‐Related Lameness Conditions 1017

words they have a regular rhythm. All other symmetrical LH LF LH LF
gaits move with right and left symmetry (both fore and
VetBooks.ir the hind limbs.
hind), but the forelimbs do not move in symmetry with
In asymmetric gaits, the footfalls of a pair of feet are
unevenly spaced in time. The canter and gallop are exam­ RH RF RH RF
ples of asymmetric gaits. Each asymmetric gait also has
17
two forms; for example, the right and left lead canter. Lateral Diagonal
This asynchrony makes it more difficult to evaluate
lameness because one must remember the movement in
one form and compare it to the other form that must be LH LF LH LF
subsequently observed. It has been shown that weight‐
bearing pain is displayed at the trot as asymmetry well
18
before the asymmetric gait is substantially altered.
Therefore, most descriptions of lameness evaluation are
focused on symmetric gaits, most commonly the trot. RH RF RH RF
The horse performs many symmetric gaits including
the walk, running walk, rack, paso largo, paso corto, Transverse Rotary
classic fino, paso llano, sobreandando, marcha picada,
marcha batida, fox trot, tölt, pace, stepping pace, trot, Figure 9.57. Footfall sequences in four‐beat gaits. Arrows
passage, and piaffe. The coordination between the indicate the order of footfalls. LH, left hind; RH, right hind; LF, left
hindlimbs and the forelimbs, the speed of progression, front; RF, right front. Source: Reprinted with permission, The
the relative durations of stance and swing phases, and Dynamic Horse, Sport Horse Publications, 2004. Reproduced with
the presence or absence of aerial phases distinguish the permission of Cambridge University Press.
symmetrical gaits. 10
contralateral forefoot. The marcha batida is an example
17
Two‐Beat Gaits: Diagonal (Contralateral) vs. Lateral of a diagonal sequence gait.
(Ipsilateral) Synchrony
The two‐beat gaits of horses use a diagonal (con­ Regular Rhythm vs. Lateral Couplets vs. Diagonal
tralateral) or lateral (ipsilateral) pattern. In the trot, Couplets
there is diagonal (contralateral) synchrony, whereby the Lateral sequence gaits can be further divided into
forelimb and the contralateral hindlimb move in relative regular rhythm vs. lateral couplet vs. diagonal couplet
synchrony with a period of suspension separating the gaits.
diagonal stance phases. 11,14 Regular (or square) rhythm gaits have a time interval
In the pace, there is lateral (ipsilateral) synchrony between ipsilateral hindlimb and forelimb footfalls of
whereby the forelimb and the ipsilateral hindlimb move exactly one‐quarter of the stride duration.
in relative synchrony and each lateral stance phase is Lateral couplets occur when the time between the
followed by a period of suspension. 10,14 Both the trot ipsilateral footfalls of the hind‐ and forelimbs occurs in
and pace have a suspension phase, which makes the less than one‐quarter of the stride duration. Lateral cou­
gaits relatively uncomfortable and more difficult for the plet gaits, such as the rack, have footfalls of a given fore‐
rider. Because of the suspension phase, the vertical and hindfeet on the same side of the body related in time
ground reaction force of each limb is greater than dur­ as a pair.
ing other gaits at equivalent speed. These gait character­ Diagonal couplet gaits, such as the fox trot, have
istics increase the severity of the observed lameness, footfalls of the fore‐ and hindfeet on the opposite sides
particularly in weight‐bearing lameness. of the body related in time as a pair. Diagonal couplets
occur when the time interval between the ipsilateral
footfalls of the hind‐ and forelimbs occurs in greater
Four‐Beat Gaits than one‐quarter of the stride duration (Figure 9.58). 10,17
Most symmetric gaits, other than the trot and pace,
are four‐beat gaits. Each hoof contacts the ground separately Gaits Other Than the Walk, Trot, Pace, and Canter
in a four‐beat gait. The footfall sequence may be lateral,
11
diagonal, transverse, or rotary (Figure 9.57). There are There are many symmetric gaits that can be difficult
no known rotary gates in the horse. to evaluate for a variety of reasons, primarily because
most practitioners have not had as much experience
evaluating these gaits. In these other symmetric gaits, the
Lateral vs. Diagonal Sequence Gaits fore‐ and hindlimbs are generally moving symmetrically,
In a lateral sequence gait, the order of footfall is LH, LF, but the timing of the fore‐ and hindlimbs varies depend­
RH, RF. Lateral sequence gaits have the footfall of a given ing on the specific gait. These gaits do not have a typical
hindfoot followed by the footfall of the ipsilateral forefoot. suspension phase and usually have at least one foot on
The fox trot is an example of a lateral sequence gait. the ground at all times.
In a diagonal sequence gait, the order of footfall is These other symmetric gaits fall in a virtual contin­
LH, RF, RH, LF. Diagonal sequence gaits have the foot­ uum from the trot, which has a diagonal (or contralateral)
fall of a given hindfoot followed by the footfall of the symmetry, to the pace that has a lateral (or ipsilateral)