In today’s horsemanship, the lateral stress on equine limbs in riding horses is again very much ignored factor. Understanding this will help you keep your horse sound and it will prolong his duration in service.
In layman’s terms, the flexibility of horse’s joints is designed more or less “lengthwise” and much less “sideways”. Even though the skeletal structure of a human is very much similar to the horse, we have much more sideways flexibility in joints than the horse. However, the most important fact in flexibility is that horses are literally walking (running) on toes (fingers). In other words, if you check your fingers, the first two joints of the first three links have almost no flexibility to the side. It is finally in the third joint (in the horse the ankle – fetlock), where we find some flexibility however, in us humans significantly more than by the horse. Again in the wrist (by the horse the so-called “knee” (carpus)) we have much more flexibility to the side than the horse. The above all mentioned joints (bones and ligaments involved) in horses are the ones that get abused the most (especially in the fixed position) when we ignore the factors of lateral stress, which is closely tied to the type of surface on which we are riding the horse. In the hind legs the most abused joint is the stifle (in human the knee), mainly the ligaments involved (joint capsule as well), which is for most part the first one to get sore since it also suffers by the altered movement of the horse caused by the weight of the rider. The stifle injury is in most cases the primarily injury in riding horses. For most part it is ignored, because we diligently ride horses in both direction, hence both stifles get sore equally, thus there is no apparent lameness (horses just do not want to put the hind end under and use it, do not want to gallop on one lead etc.). On account of the injured (sore) stifles, the horse will favor the hind legs; will travel more on the forehand, which will eventualy result into more serious injuries of the forelimbs.
The three major factors that are playing an important role in the lateral stress are, the riding surface, sharpness of turning and the speed in which the horse is moving. The speed and the sharpness of the turn will determine the degree of the angle that the body of the horse forms with the ground. The faster we are going in the turn, the sharper the angle and greater the stress sideways on joins, bones and ligaments . When we are riding a horse in the turn on a hard surface, the hoof stays parallel to the ground, though the body is in an angle, henceforth, the joints must flex sideways. The sharpness of turn and the relevance of the speed in which it is performed should determine the depth of the working surface. Henceforth, the barrel racing horse needs much more deeper surface than for example the dressage horse. I have seen that the barrel racing people for most part going by this “rule”, but not the dressage people. In most dressage riding arenas the surface is very shallow and hard despite the fact that the dressage horse spends much more time working in turns than the barrel racer. Henceforth, the time that the horse spends working in turns is also a great factor. The longeing on a hard (insufficiently deep) surface will definitely bring an early end to the working career of your horse.
Most common injuries resulting from the extreme or prolonged lateral stress are:
In hind legs the stifle, most of the time it is the initial injury that triggers the overstress of the forelimbs.
In front legs causing the navicular injury, ringbone, side-bone, splints, ankles and in higher speeds the “knee” injuries.
The prevention of the above injuries, as well as, the reduction of the lateral stress consist of the following:
Proper riding surface, adequate riding in balance and suitable shoeing (no squared toes). The reduction of the movement to the side/turning will also benefit the horse, especially if he already has some soundness problems.