We’re all familiar with stories of horses that foundered in a “good foot” when the opposite leg had a serious and painful problem like a fracture. This is an extreme example of compensation — shifting weight to counteract an area of pain. Other situations are not as dramatic, but the long-term result makes getting to the bottom of a lameness problem a major piece of detective work.
The horse is an absolute master of compensation. By redistributing weight among structurally sound portions of his body, he can move in a way that will fool most observers into thinking nothing is wrong. However, studies with treadmills and slow-motion cameras have documented several predictable patterns.
Pain in both front feet is difficult for the naked eye to detect (see Bilateral Lameness, May 2001). However, studies confirm the most consistent changes to look for are the horse holding his head more rigidly and a shorter, quicker, more jarring gait, as the horse tries to unload his feet as quickly as possible.
Most people think the horse will unload pain in a front leg by overloading the opposite front. While this does occur, it’s actually the opposite hind leg that takes most of the force. The pattern with a right-front soreness would therefore be to switch more weight to the left hind and the left front, with the left hind bearing most of the overload. If the lameness is mild or chronic, he may even appear to be more off in the left hind — so much so that, in time, he actually may become more lame in the left hind as the strain from compensating with this leg takes its toll.
Of course, the horse’s stride will shorten in the lame front leg, with the opposite front usually shortening as well to keep the strides symmetrical. However, if you watch the fetlocks, you’ll note that there is more flexion/“drop” on the sound side, as it bears more weight. The horse’s head shows less up-and-down movement when the sore leg is in motion and will tend to be more elevated when the sore leg is in full weight-bearing position.
With a primary hind-leg lameness, studies show a different pattern. The horse compensates for the hind pain by lifting much of his weight to the opposite hind leg, but he also shortens his stride with the front leg on the same side. This, of course, makes the front leg also appear to be lame.
The matching of stride lengths to retain symmetry doesn’t occur behind, however, and the horse will move shorter on the sore hind limb than on the sound one. This is also associated with more upward movement in the sacrum on the sore side. If you watch the ankles, the fetlock on the sound side drops more, as it’s carrying more weight, just as it does up front.
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