Joints - Damage - Arthritis
Arthritis means inflammation in the joint. This inflammation can be of any cause, infection, acute trauma etc. However Degenerative Joint Disease is in fact a disorder and is common in animals and humans alike usually referred to as DJD. It is generally regarded as a non-inflammatory condition of articular cartilage and is often called osteoarthritis. There are two classifications, primary DJD which occurs where there is no known trauma or disease but is typical of the joint changes in the older animal. Secondary DJD is from some direct trauma or infection of the joint. It can also result from some systemic diseases. Articular disease comes in two categories also : inflammatory and non-inflammatory and DJD is in the latter, however there may be an intermittent inflammatory phase .
Secondary DJD and its inevitable progression to damage and painful inefficient joints can occur at any age and several factors may initiate the start of the disorder. Sadly once the process starts it cannot be reversed or cured. However the process can be slowed and relief can be provided that may result in a horse maintaining an active life. DJD is the number one reason for premature horse retirement.
Joints are lined by specialized tissue, called hyaline cartilage that is vital to smooth joint function. This cartilage can become frayed and damaged due to the mechanical wear, the normally smooth glistening cartilage becomes eroded and thin, ultimately exposing bone and causing pain. With more chronic cases, the soft tissue supporting structures can become thickened which results in a decreased range of motion of the joint. DJD is not a condition of articular cartilage alone, the synovial membrane which lines the joint cavity, is also affected.
The key is the extent of the progress and acting early so that it can be held at a point that the horse is pain free and still useful. While it cannot be reversed it can be stopped and symptoms alleviated.
The number one cause is trauma, either a direct one off or repetitive concussive forces. The most common is the latter and various factors are involved in the intensity of the forces. Right at the start a horse should be analysed for conformation defects. If a career is planned for racing, jumping, dressage etc, then an experienced veterinarian should assess whether the conformation is strong and correct enough for the horse to pursue the chosen career to the highest levels. Over taxing an unsuitably built horse is likely to produce DJD and maybe a decision not to pursue a particular path may mean that given an easier sport, DJD can be delayed or even prevented.
Good intelligent shoeing can assist , but a farrier should not try and correct a deviation of the leg as that will only cause stress on joints which otherwise may not be susceptible. Good support for the actual structure that the horse has may alleviate the pressures on the joints. Balanced level feet with correct angles are vital to assist prevention, on the other hand. Incorrect shoeing can often be triggering factor
Excessive workload or overly strenuous training can be a cause but the key factor is the surface the horse is worked on, trauma from concussion is the most common cause of DJD in an earlier onset. The old fashioned idea of trotting eventing horses out on the roads to” harden them up”, is typical of the lack of understanding of what brings a horse to an early end of its competitive life.
The desire to have a workable all weather surface, whether it be an arena or track, that is level and firm throughout the year, has resulted in hard sand or cinders etc being used with no thought to cushioning the strike of the leg . Many are built as though they were a road and a shallow sand surface is placed on top. To avoid impact resistance, some consideration must be given to cushioning that surface if the horse is not to start the negative processes towards DJD. Overseas surfaces are inherently deeper, softer, and sand being added to rubber, soft chips, a mix of sand and rubber / plastic, or the European fibre sand is utilised. Indoor surfaces are often peat.
The hoof moves forwards downwards, and rapidly decelerates when brought in contact with the ground. It’s this deceleration and strike and causes the concussive effect which can be damaging to joints and bones. The term impact resistance describes the ability of the footing to absorb that concussive effect, therefore hard surfaces have high impact resistance.
Sheer resistance describes the ease with which the footing is displaced by a shearing (rotational) force. When the leg is pushing against the ground to generate propulsion, the toe tends to rotate into the surface. The shear resistance of the footing should be low enough to allow the toe to dig in as the hoof pushes against it, reducing tension in the distal check ligament and reducing pressure of the deep digital flexor tendon on the navicular region. The shear resistance can, however, be too low. For example deep soft dry sand ( as above the tideline at the beach), the ground does not offer sufficient resistance to the hoof pushing against it. Instead, the surface gives way during push off and the muscles have to work harder to generate propulsion. As a consequence of having to work harder, the muscles can become fatigued more quickly and this predisposes the horse's ligaments and tendons to injuries. Surfaces that are deep and soft will have low impact resistances but very deep heavy soft sand may be detrimental to ligaments and tendons as they will fatigue quicker with the effort of moving the legs through such a surface.
The negative effect of deep sand can be reduced by adding water which will improve the shear resistance as the foot moves through the sand, for example being ridden along the edge of the waterline on a beach is an improvement from the deeper dry sand and it still can provide a softer surface than hard dry sand. . The answer lies in the middle, with low impact resistance, as suggested from using wood, fibre, rubber and other synthetics etc , hard and/or dry sand is the worst option and most likely to initiate the process of DJD. The depth of the hoof print is a good indicator of the impact resistance, the deeper the hoof print, the lower the impact resistance and the concussive effect transmitted to joints and bones.
Left: a hard surface with high impact resistance does not allow the toe to dig in during push off.
Scientific studies have shown actual measurements that impact force is much greater with sand , and can be dampened ( reduced in force) , by the addition of water or wood or fibre. Three levels of force were classified, the greatest being dense hard (asphalt), surfaces with friction damping (sand), the least being surfaces with structural damping (wood fibres).
Whilst the cheapest option maybe hard shallow sand, it may be the most expensive if it shortens the active life of the joint and bones of the horse! When veterinarians check a horse for lameness, they run it on a hard surface as the horse is much more likely to show lameness on such a surface ….. Go figure!
Direct trauma to the joint can often develop into DJD, but any injury to a joint, strains , sprains, direct impact should be investigated and monitored so that the possibility of DJD is noted before it becomes chronic.
At first the horse may not show actual lameness, but that will come eventually. Initially the usual pain signs of discomfort, ears back, grumpy reaction to being pushed to move, restless tail when moving, personality change, then shortened steps, feeling to the rider of a jarring through the horse. It then moves on into stronger reactions to pain, refusing to go and more negative responses even when handled. Sadly some of the early signs are often missed with inexperienced owners/trainers suggesting the horse be forced often with the whip. Early on there may be a mild lameness which seems to come and go. It gets better with a turn out to pasture but returns and increases the harder the horse is worked. If the joint has a capsule that is distensible then some swelling and maybe heat is seen and felt. But if the joint is one that is contained by strong ligaments and or tendons, then swelling may not be evident. Early attention to the signs is so important as, while the process is not reversible, it can be ameliorated and held at a minor level.
To obtain a diagnosis a veterinarian may carry out an intra-articular block, using local anaesthetic. After the area of the pain is located then X-rays will be taken to help establish the cause. Also taking a sample of the fluid from the joint (synovial) can be tested to indicate the presence of arthritis. This can also indicate the extent of the degeneration by the count of the cartilage and bone cells. Possible bone fractures are also detectable.
The use of x-rays alone can create misleading diagnosis, indeed in the early part of the disease very little sign of DJD may show on x-ray. Some changes may show and could mis-lead the diagnosis, so x-rays are used after other signs are confirmed, merely to assess the extent of the disease, or indeed show fractures or developmental abnormalities which may be the true cause of the pain. Bone spurs are not an indication as they can exist in pain free joints.
As stated it is not curable, it is progressive so the very best that we can do is to prevent it. As always experience is needed to successfully care for and work with a horse , if you don’t have that experience to truly provide a balanced healthy diet, a correct work or exercise regime, understand conformation and shoeing , provide the specific care after trauma or injury, then seek qualified and expert assistance . Lack of education and knowledge creates many of the unnecessary chronic conditions in a horse.
So from the above causes you can deduce that to prevent the onset of DJD, start from the earliest days and provide a good balanced nutrition to maximise quality bone and joint development, before breaking in a horse should be assessed for his conformation, and be targeted to be utilised in a way that is appropriate to that confirmation. Ongoing he needs to be well shod (balanced and level and true to his angles) by an experienced person, in a way to reduce stress and concussive forces to the joints. The work requirement should be planned so as not to be overly excessive in the younger years and most particularly great consideration must be given to the surface that the horse is required to work on.
If DJD develops recognising the signals from the horse early can make a big difference to not allowing any further progression.
It has now been shown with scientific studies that using a nutriceutical that has the correct active ingredients in the correct quantities has a recognised beneficial effect on joints that are showing signs of DJD, and that they help to maintain the quality of the cartilage and retain its elasticity and shock absorbing qualities. Ideally a nutriceutical should be used before any chronic DJD develops, especially with horses that may be vulnerable for any of the reasons given above. Prophylactic use can assist where a horse is required to work at a young age, as with racing both harness and thoroughbred. As stated the nutriceutical must have certain active ingredients as proven by scientific test to be effective and they must be at the levels also scientifically shown to be effective.
The use of injections directly into the joint, (only carried out by a veterinarian) in combination with a suitable nutriceutical, like Flex Equine Plus , has also been scientifically proven to reduce the negative reactions to DJD. Indeed this combination has been proven to reduce the number of injections required, and therefore the cost. Likewise intra- muscular injections of products like Pentosan in combination with the same high standard nutriceutical can have similar benefits for horses not quite at such a level of the disease. Varied lengths of paddock rest can prolong the active use of the horse but as discussed a chronic condition is not reversible and becomes a maintenance regime to reduce the level of discomfort and achieve some extension of the horse’s competitive years.
Reference’s for sources for this article :
M Cruz DVM, MVM, Msc, DrMedVet
A.J Lipowitz, C.D. Newton
E.Barrey, B. Landjerit, R Wolter Ecole Nationale Veterinaire d’Alfori France, Laboratoire de Biomecanique de L’ENSAM
R.Lamberski, R A Lobos, Dr. D J Burba
Dr. H M Clayton BVMS, PhD, Diplomate Michigan State University.
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