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

Abstract

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 hind limb. Conclusion 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.