Why working on the forehand can be a horse killer

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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.

An unaffected subchondral bone.
An unaffected subchondral bone.

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.

Unaffected palmar subchondral bone site from a sample in the group of horses with mild sclerosis. Non-calcified articular cartilage is present at the bottom (arrowhead). The interface of the calcifies cartilage and bone can be seen in places (arrows).
Unaffected palmar subchondral bone site from a sample in the group of horses with mild sclerosis. Non-calcified articular cartilage is present at the bottom (arrowhead). The interface of the calcified cartilage and bone can be seen in places (arrows).

The next picture shows subchondral bone with microfracture lines and early collapse.

Subchondral bone with microfracture lines and early collapse in a sample from the group with severe sclerosis and focal rarefaction. Note multiple cracks and fragmentation of bone with formation of gaps within fracture lines.
Subchondral bone with microfracture lines and early collapse in a sample from the group with severe sclerosis and focal rarefaction. Note multiple cracks and fragmentation of bone with formation of gaps within fracture lines.

The next picture shows a higher magnification of the developing microfractures observed on the previous picture.

Higher magnification of arca along the developing microfracture in the previous picture. Note mismatched surfaces (arrows) and fragmentation of margins indicating fracture gap has collapsed. Osteoclastic erosion sites (arrowheads) were seen in larger developing cracks and indicated there had been remodeling at the site.
Higher magnification of arca along the developing microfracture in the previous picture. Note mismatched surfaces (arrows) and fragmentation of margins indicating fracture gap has collapsed. Osteoclastic erosion sites (arrowheads) were seen in larger developing cracks and indicated there had been remodeling at the site.

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.

Incompletely ground sample from group with advanced lesions. Enlarged vascular canals and resorption sites (arrows) indicate there has been remodeling around the more chronic defect. 
Incompletely ground sample from group with advanced lesions. Enlarged vascular canals and resorption sites (arrows) indicate 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.

Higher magnification of microfracture gap with entrapped vessel. Note the smooth edges on ground fragments indicating chronic wear on the surface.
Higher magnification of microfracture gap with entrapped vessel. Note the smooth edges on ground fragments indicating chronic wear on the surface.

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.

Subchondral bone microfracture at the site of collapse and indentation of cartilage (arrowheads) in a sample from the group with advanced lesions. A fracture line through the calcified cartilage, (lower left) is associated with further infolding. The layer of bone above the microfracture has multiple fragmentation lines and a compacted appearance (outlined by arrows).
Subchondral bone microfracture at the site of collapse and indentation of cartilage (arrowheads) in a sample from the group with advanced lesions. A fracture line through the calcified cartilage, (lower left) is associated with further infolding. The layer of bone above the microfracture has multiple fragmentation lines and a compacted appearance (outlined by arrows).

A closer view is underlining the reality of the damage.

Higher magnification of subchondral bone microfracture with collapsed matrix from the previous picture. Bone matrix above the microfracture line has multiple fine cracks (arrowhead) and a compacted arrangement. Also note continued fragmentation of fracture margins in the gap.
Higher magnification of subchondral bone microfracture with collapsed matrix from the previous picture. Bone matrix above the microfracture line has multiple fine cracks (arrowhead) and a compacted arrangement. Also note continued fragmentation of fracture margins in the gap.

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.

A horse in balance, left, and at right, the outline of a photo of a horse heavily loaded on the forehand.
A horse in balance, left, and at right, the outline of a photo of a horse heavily loaded on the forehand.

scienceofmotion.com

Jean Luc Cornille

Jean Luc Cornille M.A.(M.Phil) has gained worldwide recognition by applying practical science to the training of the equine athlete. Influenced by his background as a gymnast, Jean Luc deeply understands how equine training can be enhanced by contemporary scientific research. A unique combination of riding skill, training experience and extensive knowledge of the equine physiology enables Jean Luc to "translate" scientific insights into a language comprehensible to both horse and rider. This approach has been the trademark of his training. - read more about Jean Luc

One thought on “Why working on the forehand can be a horse killer

  • January 5, 2021 at 1:23 pm
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    Having seen many styles of showing horses over my many years, I have to wonder if any trainers watch horses on their own – horses in the pasture free to run, jump and play. I spend more time watching than riding. Here’s what I see: horses don’t travel with their noses at their knees or above their withers unless there is a reason. They carry their necks mostly level at all gaits. A high head is usually excitement or looking at something. A low head is typically a search for food or chasing something small. Horses can balance themselves and perform fantastic moves without hurting themselves, not that they don’t slip and fall, particularly youngsters, but the idea that humans have to balance them ignores the fact they have survived for millennia without us. We need to balance ourselves as riders to stay out of the horses way. I think we should stop overworking horses by thinking they need to be “trained” 6 days a week, and pay attention to what the horse is telling us. Horses need time off to be horses, to rebuild bone, rest muscles, and de-stress mentally. It’s good for their health and longevity.

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