Performance Ponies, Health, Performance Horses
Aligning the Front End
A horse is more likely to have problems with it’s front legs than the back ones because its heavier front half carries 60-65% of its weight.
For proper hoof flight, all parts of the moving leg must be aligned, beginning with the shoulder. When we look at a horse from in front, we should see a straight line down the forearm, through the knee, and into the pastern and hoof. The distance between the legs at the chest should be the same as the distance between the feet on the ground. Few horses have perfect conformation, and the amount of deviation has a strong bearing on hoof flight abnormality and the potential for injury and joint disease.
Proper alignment in the front end begins in the shoulder. What this means is that the slope of the shoulder should match the slope of the pastern and hoof, with forearm and cannon bones forming a straight line through the knee until reaching the pastern. This alignment has all of the bones fitting neatly together with properly aligned joints.
One of the most troublesome abnormalities in front limb joint conformation is toe out. These horses have pastern, knee, and/or shoulder joints out of alignment, with the toes pointing out instead of forward. This is not a big problem as long as the horse remains still, but when he moves, particularly at the trot, the abnormality causes serious hoof flight problems. The hooves will wing inward, sometimes striking the opposite leg during the flight phase. Injury, accompanied by lameness, is often the result.
The other problem some horse’s face is toe in, where the toes point inward instead of straight ahead during the ground contact phase. As the horse travels, the hooves will swing outward during the flight phase. While the horse doesn’t kick itself, the abnormal hoof flight pattern puts undue strain on joints.
Base-wide horses (those that stand with their hooves farther apart than the legs are at the chest) often have narrow chests, and are often toe out as well.Base-narrow horses stand with their hooves closer together than the legs are at the chest, and usually have wide chests. They tend to be toe in as well.
The pasterns are key shock-absorbing joints, and as a result must be strong, yet pliable. The pastern is made up of two bones between the fetlock joint and the hoof, and the joint between those two bones.
Long pasterns tend to have these two bones longer than normal, and the pasterns drop more horizontally especially during disciplines such as racing and jumping.
Pasterns that are too short remain fairly upright even with high stress. This results in too much concussion travelling up the leg because these less flexible pasterns are less efficient shock absorbers.
Other joint alignment problems originate in the knee or carpal joint. One that was previously thought to be quite serious is bench knee. This means the forearm and cannon bone are not properly aligned. The bench-kneed horse will have the forearm entering the knee on the inside or medial aspect, while the cannon bone below the knee joint will exit on the outside or lateral aspect.
Though it has commonly been thought that bench knees put a horse at serious risk for injury especially in high-stress disciplines, recent research suggests this might not be the case.
Two other conditions of the knee joint that can alter normal hoof flight and weight bearing and raise the injury potential are being over at the knee (with the forearm ahead of the cannon bone viewed from the side, also known as bucked knee), or being behind at the knee (the reverse of over at the knee, also called calf knee). Of the two, calf knee is the more serious because of the stress on tendons and ligaments that run down the back of the leg, and because of the predisposition to chip fractures from overextension of the joint.