It is common for horses to have different high hooves or different high fittings on their four legs. We know less about how this affects their movement patterns and the load on the legs.
In people, it has been known for some time already about how differing length of legs may produce an uneven load, sometimes with stress injuries as a result. Up until now, it has been unknown whether this also applies to horses. Knowledge of how a leg length difference affects the pattern of movement is also important for correct lameness evaluation of horses.
Researchers from the Swedish University of Agricultural Sciences, together with international colleagues, have therefore investigated how differences in bone length affect the symmetry of the horse's movement pattern in trot. In the study, eleven horses were examined that got 15 or 30 mm raising of a hind leg with the aid of specially made hind limb boots, "orthotic lifts." The symmetry in the motion pattern was subsequently measured with a sensor system.
The study showed that the elevation of a hind leg gave the horses an asymmetry in the movement pattern, corresponding to an increased load on the shorter leg and a stronger push-off from the long leg. This is in line with what was previously seen in humans. Therefore, different leg lengths in horses may lead to similar strain injuries seen in humans. The study also shows that it is important to take into account any differences in bone length in order to correctly assess lameness in horses.
This study was financed by Formas.
Link to the publication
Jodi Vertz, Diana Deblanc, Marie Rhodin, Thilo Pfau (2018) Effect of a unilateral hind limb orthotic lift on upper body movement symmetry in the trotting horse. PLoS ONE, 13(6): e0199447.