Effect of induced unilateral synovitis of distal intertarsal and tarsometatarsal joints on sagittal plane kinematics and kinetics of trotting horses.

This study explores how unilateral synovitis in horse’s lower joints can affect their movement and how they compensate for this pain. The findings reveal that horses manage mild hind limb lameness by reducing the airborne phase of their stride and not by loading more weight onto the unaffected limbs.

Research Purpose

The main objective of this research was to analyze the impact of unilateral synovitis, induced in the distal intertarsal and tarsometatarsal joints of horses, on their locomotion. Also, the compensating effects of the other limbs were examined.

• The study was performed on four clinically normal horses.
• The researchers ran gait analyses to study how the horse’s walk or trot (locomotion) changed after inducing lameness.

Research Methodology

The researchers used kinematics, a force plate, and inverse dynamic analysis methods to understand the movement of horses.

• Gait analyses were performed initially when the horses were in normal condition(without lameness) and later after inducing lameness by injecting an endotoxin into their right distal intertarsal and tarsometatarsal joints.
• The main variables for the study- stride and different movement related parameters during two conditions (sound and lame) were analyzed for differences.

Research Findings

The study showed a change in the locomotion of horses when they were lame.

• A decrease in the range of motion of the tarsal joint, peak vertical force, and vertical impulse were observed during lameness.
• The mechanical deficits witnessed were a decrease in negative work by the tarsal extensors during the early stance phase and a reduction in positive work by the tarsal extensors during push-off.
• No compensatory changes were observed in other joints within the lame hind limb during the stance phase.
• The vertical impulse in the diagonal forelimb decreased but no significant changes in forces or impulses in the ipsilateral forelimb or contralateral hind limb were recorded.

Research Conclusions

The findings confirmed that in order to manage mild unilateral hind limb lameness, horses reduce the airborne phase of their stride rather than increase the loading of the compensating limbs. In other words, they preferred to keep their lame limb in the air for a shorter duration rather than put more weight on the sound limbs.