What is Equine Arthritis & Degenerative Joint Disease
Arthritis means inflammation in the horse’s joints, this inflammation can be from any cause: infection, trauma etc. However Degenerative Joint Disease is a disorder, common in animals and humans alike usually referred to as DJD, it is often used as an overall definition for all joint disorders, although there are various forms of arthritis and different reasons for the development of such.
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 direct trauma or disease but is typical of the joint changes in the older animal; secondary DJD- from direct trauma or infection of the joint. Secondary DJD and its inevitable progression to inefficient joints can occur at any age and several factors may start the disorder. Sadly once DJD starts, it cannot be reversed or cured. However the process can be slowed & relief can be provided that may result in a horse maintaining an active life. DJD is the number one reason for premature horse retirement, 60% of all lameness is due to DJD. Joints are lined by specialised tissue, called hyaline cartilage that is vital to smooth joint function. This cartilage can become frayed and damaged due to the mechanical wear, 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. If left unattended joints will become swollen and sore and eventually new bone is created to strengthen the surface (a process called sclerosis) and extend its margins (bone spurs and osteophytes). In its final stages, if left unchecked, arthritis causes the fusing of equine joints. 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 symptoms can be alleviated.
What Causes The Damage to the Joints?
The main cause is trauma, either a direct one off or repetitive concussive forces, the most common is the latter, that is the force up the leg from each step the horse takes. The likelihood of DJD comes from: poor confirmation, genetic pre-disposition, surfaces too hard, overworking on harder surfaces, poor shoeing, direct accidental damage to a joint, infection of a joint, puncture of a joint or old age.
How Can DJD be Avoided
So to prevent the onset of DJD, start from the earliest days and provide good balanced nutrition to maximise quality bone and joint development, before breaking in a young horse should be assessed 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 chosen career. Over taxing an unsuitably built horse is likely to produce DJD and therefore a decision not to pursue a particular path may mean that given an easier sport, DJD and pain for the horse can be delayed or 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 with balanced level feet and correct angles are vital to assist prevention, on the other hand, incorrect shoeing can often be a trigger. Ongoing he needs to be well shod, to reduce stress and concussive forces to the joints, shoes should be selected for the conditions of work, ie heavy road shoes should not be used unless really necessary and the horse is strong enough to carry the weight. Care with the development of the young horse, not breaking in too early, balancing the workload with the development of maturity while being aware of the type of horse and its future. Larger heavier warmbloods mature much later than thoroughbreds. Excessive workload 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 younger horses. The idea of trotting horses out on 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. If DJD develops, early recognition can make a big difference to preventing progression.
The Importance of the Surface Under the Horse’s Feet
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 thought 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, plastic, or now fibre sand is utilised. 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 be too low, eg 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.
Left: a hard surface with high impact resistance does not allow the toe to dig in during push off.
Centre: a surface with moderate impact and shear resistance allows the toe to dig but then offers resistance as the hoof pushes off.
Right: a soft surface with low impact but low shear resistance and gives way and does not offer sufficient resistance as the hoof pushes off.
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.
Scientific studies actually show 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 joints 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.
What are the Signs of Joint Pain?
At first the horse may not show actual lameness, initially the usual pain signs of discomfort, ears back, grumpy reaction to movement, restless tail when moving, personality change, then shortened steps, horse feels wooden. It then moves on into stronger reactions to pain, refusing to go, 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 intermittent lameness. It gets better with a turn out, but returns and increases with work. 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 DJD can be ameliorated and held at a minor level.
To obtain a diagnosis a veterinarian may carry out a nerve block. After the area is located, X-rays will be taken. Also taking a sample of the fluid from the joint (synovial) can be tested to indicate the presence of arthritis. This can indicate the extent of the degeneration by the count of the cartilage and bone cells. The use of x-rays alone can create misleading diagnosis, 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, to assess the extent of the disease, or other issues which may be the true cause of the pain. Arthroscopy is an option, usually done by a specialist, where an optical tube is inserted into the joint and gives the veterinarian a view of the joint and its issues. Changes can be seen as an area of dullness on the cartilage, colour change from glistening white to a mottled grey or even yellow, it gives the most definitive diagnosis of arthritis. However this is an invasive procedure and has all the risks of that invasion.
What Can be Done to Help a Horse with DJD
It is not curable, it is progressive, but it can be held, of course in the first instance the best we can do is to prevent it, as discussed above. A quick response to the signs is important. Scientific studies have now shown that using a nutraceutical containing the correct active ingredients in correct quantities does have a recognised beneficial effect on joints 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 prior to DJD developing, 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. The nutriceutical must have certain active ingredients, at the right levels proven by scientific tests. For example the recommended level of glucosamine is 1200 mg per day, but manganese is needed in the formula to convert that to an active called GAGS as that is the substance that improves the cartilage. Perna Mussel, while effective in other animals and humans is not so effective for horses and a high quantity is needed. The newest science on a supplement is the exciting addition of Denatured Collagen Type II which in conjunction with the other proven actives of glucosamine and chondroitin has increased the therapeutic response.
For established DJD, injections directly into the joint, 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. Overall it becomes a maintenance regime to reduce the level of discomfort and achieve some extension of the horse’s competitive years. The main solution is to prevent the onset and safeguard joints with the next generation Flex-Equine Plus - protect the younger horse from concussive damage and put back the spring in the older horse! It has the right amounts of scientifically proven ingredients its a full formulation of glucosamine, chondroitin, manganese, gelatin, zinc and copper and now with newly discovered Undenatured Collagen Type II.
Reference’s for sources for this article:
M Cruz DVM, MVM, Msc, DrMedVetA.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.
Some of the scientific references ( for a fuller list see the product page Flex Equine Plus)
Therapeutic efficacy of undenatured type-II collagen (UC-II) in comparison to glucosamine and chondroitin in arthritic horses.Gupta RC, Canerdy TD, Skaggs P, Stocker A, Zyrkowski G, Burke R, Wegford K, Goad JT, Rohde K, Barnett D, DeWees W, Bagchi M, Bagchi D. Jvet Phamacol -2009
The Effect of Glucosamine and Chondroitin on Stressed Equine Cartilage Explants. R.S.A Harlan MS, R.C.A Haut PhD, M.W.A. Orth PhD JNL Equine Science Volume 32 Ussue 1 Jan 1012
Effects of Chondroitin and Glucosamine Sulfate in a Dietary Bar Formulation on Inflammation,0 Interleukin-1CEB2, Matrix Metalloprotease-9, and Cartilage Damage in Arthritis. M. Chou*,Nathalie Vergnolle ,Jason 0 J. McDougall,John L. Wallace,Stephanie Marty,Val Teskey and AndreG. Buret. Exp Biol Med April 2005 Vol 230 No 4
Effects of glucosamine hydrochloride and chondroitin sulphate, alone and in combination, on normal and interleukin-1 conditioned equine articular cartilage explant metabolism. Dechant JE, Baxter GM, Frisbie DD, Trotter GW, McIlwraith CW.
Equine Vet Jnl 2005 May 37 (3) :227-31
Spot all the Joints!