By assessing the vertical amplitude of movement of the tuber coxae of
each hemipelvis throughout the stride and comparing the left and right
hemipelvis movements
By assessing the extension angle of the fetlock (fetlock drop) of each
hindlimb during maximum weightbearing and comparing left and right
hindlimbs
By assessing the position of the head during the weightbearing phase of
each hindlimb and comparing between left and right hindlimbs
By assessming various joint angles and stride length and foot flight
characteristics (less useful).
An important principle in the recognition of hindlimb lameness is the
concept of the pelvic hike or hip hike. Since the horse has two “hips” and
only one pelvis, the term pelvic hike is more accurate. Pelvic hike is the
vertical elevation of the pelvis when the lame limb is weight bearing. In
other words, the entire pelvis “hikes” upward when the lame limb hits the
ground and moves downward when the sound limb hits the ground. It is
the shifting of weight or load that occurs as the horse tries to reduce
weight bearing (unload) in the lame limb and transfer weight (load) to the
sound limb. This difference is best observed by tracking the movement of
the top of the croup region (both tubera sacralia) throughout the entire
stride.
Many horses with hindlimb lameness (certainly not all) drift away from the
lame limb toward the sound limb. Drifting is one of the earliest adaptive
responses of a horse with unilateral hindlimb lameness, allowing the horse
to break over more easily or to reduce load bearing. Drifting may decrease
the magnitude of the observed pelvic hike, but more important, it makes
the lame side look lower than the sound side. This is why it is important to
watch the entire pelvis as a unit rather than the individual sides of the
“hips.” Many driven STBs with hindlimb lameness drift away from the lame
limb or are “on the shaft.” Horses with LH lameness have a tendency to be
on the right shaft and vice versa.
In horses with hindlimb lameness the normal symmetrical vertical
movements of both quarters, as observed by focusing on the vertical
displacement of the tuber coxae of each hemipelvis from behind the horse,
is disturbed. The quarter on the lame side will rise and fall through a
greater range of motion (increased vertical amplitude of movement of the
tuber coxae) than that of the sound limb. This is usually characterized by a
long downwards drop of the tuber coxae of the lame limb during the swingphase of the stride, followed by a fast, sudden, upwards flick, or hike of the
tuber coxae of the lame limb, during the weightbearing phase of the stride.
The degree of lameness is subjectively assessed and recorded on a
numerical scale. To help the investigator, hip markers can be applied to
aid the recognition of asymmetry of hindlimb movement in cases which are
only slightly lame (May and Wyn-Jones 1987).
Pain-related lameness will result in a reduction in the extension of the
metatarsophalangeal joint providing there is no disruption of the palmar
soft tissue supporting structures, hence making this sign a useful predictor
15-‐18
February
2016
East
London
Convention
Centre,
East
London,
South
Africa
53