The aims of this study were to quantify the morphological differences between uneven feet, and to evaluate the biomechanical locomotor consequences compared to horses with even feet, considered as normal.
Eight anatomical parameters that quantified conformational differences in the distal forelimbs of horses with a varied range of hoof asymmetries (n = 36, of which 2 were lame) were compared using discriminant analysis. Forefeet were subjectively scored for unevenness by one clinician. Kinetics and distal limb kinematics of clinically sound horses (n = 34; the 2 lame horses were excluded) were collected at trot and compared between even (n = 13) versus uneven (n = 21) forefeet and between all feet when classified as flat, medium and upright using MANOVA/ANOVA. The relative influence of contralateral differences in hoof angle and of absolute hoof angle on functional parameters was analyzed by multiple regression (P<0.05).
Unevenness was best determined by the differences in dorsal hoof angle between the forefeet. In uneven footed horses, the flatter foot showed a significantly larger maximal horizontal braking and vertical ground reaction force, a larger vertical fetlock displacement and a suppler limb spring. A steeper hoof angle was linearly correlated with an earlier braking-propulsion transition. No significant differences were found between individual flat, medium or upright feet.
The conformational differences between the forefeet were more important for loading characteristics than the individual foot conformation. The contralateral differences in vertical force could in fact imply an early, subclinical sign of lameness developing in the steeper forefoot, as these differences were smaller than those reported for subtle, clinically evident lamenesses.