The anatomy of the horse’s lower forelimb is identical with that of the hind limb. Why then is lower forelimb lameness so much more prevalent than hind limb lameness? I am referring to such common unsoundness as high ringbone, low ringbone, splints causing pain, bowed tendons, navicular syndrome, laminitis, suspensory ligament injury, proximal sesamoiditis, and sidebone severe enough to cause lameness.
All of the problems mentioned can and do occur in the lower hind limbs, but to a much less frequency than in the forelimbs, and when they do they are much less likely to cause an obvious change in gait (“lameness”).
There are several reasons:
The least most significant is that slight forelimb lameness is more obvious to the inexperienced observer than is hind limb lameness. Why? Because if there is pain in a forelimb, the horse’s head and neck serve as a semaphore, signaling that something is wrong. It goes DOWN on the less painful leg, DOWN on the better leg! So many clients have told me, “He is lame in the right front leg. His head goes down on that leg.”
Well, the reason he is putting more weight on that leg, which causes the head to drop farther than the opposite leg, is because it is less painful to do so. The horse puts more of his weight on the better leg, so the head on that side goes down farther. Down on the good leg! Get it?
However, that doesn’t explain why the incidence of lameness is so much less common in the hind lower legs than it is in the lower forelegs.
The average horse bears 60% of its body weight on the forelegs and only 40% on its hind legs. Why? Because the head and neck are so heavy, and extend out in front of the forelegs, whereas the hind legs are right under the hind quarters of the horse’s body. It’s a simple matter of balance. There’s more weight up front.
The center of balance for most horses is at the withers. This is why the forelegs suffer the damages cited above more than do the hind legs. They have to bear more weight. The hind limbs do most of the propulsion whereas the forelegs are mostly weight bearing.
But, you may ask, doesn’t the weight of the rider, behind the withers, kind of equal things out?
Well, to a degree that’s true. The saddle and rider are behind the withers but the way we train and ride so often increases the forces the forelegs are subjected to. The lower the head and neck of the horse the greater the weight placed upon the forelegs. It’s a matter of simple physics.
So, horses bred for a naturally low head carriage, like our stock horse breeds, may carry more than 60% weight up front.
Horses bred and ridden with a high poll, but flexed high in their necks, like the dressage breeds, have a reduced weight forced upon their forelimbs.
Obviously, horses ridden with a very low head position as is commonly seen in Western Pleasure classes, or, in recent years, in cutting and reining classes, have a lot of extra weight forced upon their forelegs.
All of these factors, increasing the weight placed on the forequarters, ahead of the natural point of balance, the withers, increases the likelihood of damage, greater up front than in back.
Added to this is the fact that we are breeding horses with greater agility and faster reaction time than in the past, hence greater strain. Moreover, we are starting training colts younger and younger, before their bodies are mature enough to withstand the stress of extreme athletic performance such as jumping, reining, cutting, sprinting, etc.
All of this keeps us veterinarians busy.
Is a low head position natural for the horse? If so, why does an alarmed horse immediately assume a high head position? Is it because five of the six senses are only located in the head?
What five senses? Vision (the eyes), Smell (the nose), Taste (the mouth), Hearing (the ears), and the Tactile sense (the sense of touch).
Only the last named occurs on all body surfaces. The other four require organs only found in the head. The olfactory sense, the visual sense, the auditory sense are all exquisitely developed in the horse. Its sense of smell, vision and hearing are essential, in the wild, for equine species to detect the presence of predators early enough to enable survival, primarily via the horse’s flight response.
And, in the wild, flight usually successfully ensures the horse’s survival because natural selection has endowed the horse with exceptionally fast reaction time plus an anatomy and physiology that provides speed and escape.
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