Head and trunk movement adaptations in horses with experimentally induced fore- or hindlimb lameness

The kinematic patterns of head and trunk were studied in horses during induced supporting limb lameness to understand the mechanisms horses use to compensate for lameness and to evaluate different symmetry indices for their significance as lameness indicators. Using the locomotion analysis system CODA-3 the kinematics of 11 clinically nonlame Dutch Warmblood horses were recorded while walking (1.6 m/s) and trotting (3.5 m/s) on a treadmill. A transient lameness model, evoking pressure induced pain on the hoof sole, was used to induce 3 degrees of fore- and hindlimb lameness. Peak vertical displacement, velocity and acceleration of head, withers, tuber sacrale and both tuber coxae were quantified at different phases of the stride. Changes in these variables due to lameness and symmetry indices calculated as quotients of the values during the lame and nonlame stance phase were analysed using a 2-way analysis of variance. The head, withers and tuber sacrale showed a similar sinusoidal pattern in their vertical displacement, velocity and acceleration. During both fore- and hindlimb lameness at the trot, the vertical velocity of the trunk at impact of the lame limb decreased (P < 0.05), during the lame stance phase the trunk was kept higher above the ground, maximal acceleration decreased and displacement amplitude was smaller than without lameness. Changes in movements of the head were much more expressed than movements of the withers during forelimb lameness and reversed during hindlimb lameness. At the walk, head movement patterns changed in the same way as at the trot, while withers and tuber sacrale patterns were hardly changed. Symmetry indices of all landmarks showed changes due to increasing lameness at the trot. The maximal vertical acceleration of the head and displacement amplitude of the tuber sacrale proved to be the best indicators to quantify a fore- and hindlimb lameness, respectively.