Objective—To measure the effect of subject velocity
on hind limb ground reaction force variables at the
walk and to use the data to predict the force variables
at different walking velocities in horses.
Animals—5 clinically normal horses.
Procedure—Kinematic and force data were collected
simultaneously. Each horse was led over a force plate
at a range of walking velocities. Stance duration and
force data were recorded for the right hind limb. To
avoid the effect of horse size on the outcome variables,
the 8 force variables were standardized to body
mass and height at the shoulders. Velocity was standardized
to height at the shoulders and expressed as
velocity in dimensionless units (VDU). Stance duration
was also expressed in dimensionless units
(SDU). Simple regression analysis was performed,
using stance duration and force variables as dependent
variables and VDU as the independent variable.
Results—Fifty-six trials were recorded with velocities
ranging from 0.24 to 0.45 VDU (0.90 to 1.72 m/s).
Simple regression models between measured variables
and VDU were significant (R2 > 0.69) for SDU,
first peak of vertical force, dip between the 2 vertical
force peaks, vertical impulse, and timing of second
peak of vertical force.
Conclusion and Clinical Relevance—Subject velocity
affects vertical force components only. In the
future, differences between the forces measured in
lame horses and the expected forces calculated for
the same velocity will be studied to determine
whether the equations can be used as diagnostic criteria.
(Am J Vet Res 2001;62:901–906)
Objective—To study the effect of unilateral synovitis
in the distal intertarsal and tarsometatarsal joints on
locomotion, including the compensating effects within
and between limbs.
Animals—4 clinically normal horses.
Procedure—Gait analyses including kinematics, force
plate, and inverse dynamic analysis were performed
at the trot before lameness, after which synovitis was
induced by injecting endotoxin into the right distal
intertarsal and tarsometatarsal joints. Gait analyses
were repeated 24 to 30 hours later during lameness.
Differences between the stride variables during the 2
conditions (lame and sound) were identified.
Results—Tarsal joint range of motion, peak vertical
force, and vertical impulse were decreased during
lameness. Mechanical deficits included a decrease in
negative work performed by the tarsal extensors during
the early stance phase and a decrease in positive
work by the tarsal extensors during push off. No compensatory
changes in work were performed by other
joints within the lame hind limb during the stance
phase. Vertical impulse in the diagonal forelimb
decreased, but there were no significant changes in
forces or impulses in the ipsilateral forelimb or contralateral
Conclusions and Clinical Relevance—Results indicate
that horses are able to manage mild, unilateral
hind limb lameness by reducing the airborne phase of
the stride rather than by increased loading of the compensating
limbs. (Am J Vet Res 2003;64:1491–1495)