Sclerotic thickening of the subchondral bone is a major factor in the pathogenesis of arthritis. Excessive loading and the accumulation of microdamage are thought to be important elements in the development of arthritis.
Unless one possesses a Phillips XL30 scanning electron microscope, no-one ever see microdamages or even microfractures, and therefore accept riding and training techniques that increase the load on the forelegs, lowering of the neck, driving the horse onto the bit, more forward, etc.
We often state, if a riding or a training technique is not good enough for the higher level of performances, it is not good enough for lower level horses. The same can be said about scientific knowledge. A little bit of science might be good enough to accredit simplistic theories, but if we look deeper, the magnitude of the damages questions the value of popular theories. Loading of the forelegs is the main reason for all forms of arthritis.
“Subchondral clerosis and area of bone devitalization are common in the overload arthrosis of equine athletes.” (Subchongral bone failure in overload arthrosis: A scanning electron microscopic study in horses; R.W. Norrdin and S. M. Stover, 2006; 6(3); 251-257).
Before listening and even believing in riding and training techniques that load the horse’s front legs, one might need to see how micro-cracks evolve into subchondral sclerosis and area of bone devitalization.
Thanks to the fascinating work of R. W. Norrdin and S. M. Stover and also the wonders of modern technology, above is what an unaffected subchondral bone looks like.
The next picture shows subchondral bone with microfracture lines and early collapse.
The next picture shows a higher magnification of the developing microfractures observed on the previous picture.
Bones do have a remarkable capacity of remodeling but if stress (excessive load on the forelegs) alters the bone remodeling capacity, the development of micro-cracks in the subchondral bone leading to arthritis in the cartilage is evolving right before your eyes.
The next sample is from a group with advanced lesions showing gaps in defect-containing smoothly, ground fragments of subchondral bone. The area in the white rectangle shows that there has been remodeling around the more chronic defect.
The region of interest, which is the area within the rectangle, is magnified in the next picture. The magnification shows an entrapped vessel.
The mechanism varies with the specific joint depending on the forces involved and the pattern of loading. This picture series have been made with racehorses. The lesions presented on these pictures is referred to as “Traumatic osteochodronsis”.
The problem is common in racehorses. For many, the subchondral bone damages are asymptomatic. However, the more severe forms are associated with fetlock lameness. Dressage and jumping horses are subject to less intense but similar overloading and when the riding and training technique reiterates overloading with every training session, the bone remodeling does not repair the damages and the evolution that you see leads to arthritis.
“Unload it” is the title of a recent study on human knee arthritis. Unloading it is how we restored soundness on Caesar, who suffered from arthritis between the second phalange and the coffin bone of the left hind leg. Unloading it is how we gave back mobility and life to the beautiful Diva, who suffered from double ring bone. Unload it is how we restored soundness on Manchester, who suffered from both a stifle problem and arthritis on the same joint as Caesar, but the other front leg. And the list goes on and on and on.
Since no one can see it until it is too late, it is easy to ignore the problem and keep lowering the neck and loading the horse’s front legs. The rider’s knowledge is the horse’s sole protection and therefore we continue the picture series further showing the evolution of the damages.
A closer view is underlining the reality of the damage.
It might be interesting to end this article placing side by side a horse working in balance and a horse heavily loaded on the forelegs.