When a horse is lame, he often seems to be changing his gait in the diagonal limb to compensate. Recent research has shown this to be true, but the manner in which the horse does this is surprising.

Research was conducted at the McPhail Equine Performance Center at Michigan State University’s College of Veterinary Medicine. Often in hind limb lameness diagnosis, veterinarians look for a compensatory change in the diagonal limb to indicate the horse is trying to relieve pain. Riders suspicious of hind limb injury often report a loss of “bounce” in the horse’s stride, particularly noticeable when posting the trot.

As expected, the study showed that horses changed the way they used the painful limb when trotting, exhibiting these changes at varying levels in that limb during the stance phase as the horse tried to decrease the load on the painful joint.

However, using a sophisticated gait analysis system and force plate analysis, researchers found that horses decreased the height of the diagonal limb in the airborne phase, while the stance phase in that limb was affected less than was expected. Video analysis showed an overall reduction in vertical displacement of the horse’s center of mass during the airborne phase of the trot. Interestingly, the horse accomplished this attempt at pain relief without increasing load in the opposite diagonal pair of legs