Page 164 - Adams and Stashak's Lameness in Horses, 7th Edition

130 Chapter 2

The most direct observational sign of hindlimb lame­ classification, this can be called an “impact”‐type
ness is asymmetric vertical movement of the entire pos­ hindlimb lameness.
VetBooks.ir mass on a long lever arm projecting out of the hindquar­ horse pushes off less, causing the pelvis to rise less,
When pain is greatest in the second half of stance, the
terior end (pelvis) of the horse. The horse has no large
resulting in a difference in the high positions of the pel­
ters, so the simple mechanism achieved by altering head
movement to adjust forelimb weight‐bearing is not vis (Figure 2.121). It is lower after lame limb pushoff.
available to the horse with hindlimb lameness. Other For purposes of classification, this can be referred to as
adjustments must be performed. To decrease force on a “pushoff”‐type hindlimb lameness.
the hindlimbs, the pelvis either falls less (like dropping a Hindlimb lameness can be both impact and pushoff,
ball from a lower height), if the pain is greatest in the which becomes more common as hindlimb lameness
first half of stance, or rises less, from decreased hindlimb increases in severity. Hindlimb lameness can also be
vertical propulsion, if pain is greatest during the second impact on one side and pushoff on the other, a bilateral
half of stance. As the severity of hindlimb abnormality lameness, but this is not common. Unlike forelimb lame­
increases, both decreased fall and decreased rise (impact ness, where at moderate speeds most lameness is of the
and pushoff lameness) are seen. The adjustments made impact type, for hindlimb lameness a predominant
by the horse to decrease fall and to decrease rise of the impact‐ or pushoff‐type lameness occur with approxi­
pelvis are different. mate equal frequency. This is probably because the
Decreased fall of the pelvis results in a difference hindlimb acts as both a propulsive force during pushoff
in low positions of the pelvis near midstance, lower and a braking force during impact even at moderate
(i.e. closer to the ground) on the not lame or less lame speed of movement. There is objective evidence that
hindlimb, if the pain is primarily in the first half impact and pushoff hindlimb lameness have different
of hindlimb stance (Figure 2.120). For purposes of vertical and horizontal ground reaction force profiles.
6

A C

B

Diff Min Pelvis
D

Lame limb stance

Figure 2.120. Overall vertical pelvis trajectory pattern for horse beginning of stance of the left hindlimb) is zero. Lowest pelvic
with impact‐type hindlimb lameness or lameness with pain greatest position occurs during stance of the not or less lame hindlimb. Diff
in the first half of hindlimb stance. Peak (maximum) vertical pelvic Min Pelvis or first minimum pelvic height (B: during stance of the
position before right and left hindlimb stance is the same. Diff Max right hindlimb) minus second minimum pelvis height (D: during
Pelvis or first maximum pelvis height (A: near beginning of stance of stance of the left hindlimb) is a positive value for right hindlimb
the right hindlimb) minus second maximum pelvic height (C: near lameness (and a negative value for left hindlimb lameness).

D
Diff Max Pelvis B

Pushoff of
left hind limb
A Pushoff of C
right hind limb

Lame limb stance
Figure 2.121. Overall vertical pelvis trajectory pattern for horse maximum pelvis (near beginning of stance of the right hindlimb, D)
with pushoff‐type right hindlimb lameness or lameness with pain minus second maximum pelvic height (B: near beginning of stance of
greatest in the second half of right hindlimb stance. Peak (maximum) the left hindlimb) is positive. Lowest pelvic position occurs during
vertical pelvic position after pushoff of left hindlimb (D: before impact stance of right and left hindlimbs. Diff Min Pelvis or first minimum
of right hindlimb) is greater than vertical pelvic position after pushoff of pelvic height (A: during stance of the right hindlimb) minus second
right hindlimb (B: before impact of left hindlimb). Diff Max Pelvis or first minimum pelvis height (C: during stance of the left hindlimb) is zero.