As we work our horse, we put strain on their joints. Under normal conditions small stresses and strains promote the body’s natural repair processes and ultimately lead to strengthening of the tissues. However, during hard work such as eventing or repeatedly riding and jumping on hard ground, the demand for repair may outstrip the supply, leading to a gradual deterioration of the horse’s joints. Something that can help to be prevented by feeding a targeted supplement.
The structure of joints is designed to prevent abrasion and damage to the bones. However, the major weight bearing joints such as the knees, fetlocks and small joints of the hock are particularly prone to degeneration due to the amount of work they perform. These joints are where two bones meet to allow a hinge-like movement. Each of the bones has a covering of articular cartilage to create a slippery surface to prevent abrasion and absorb concussion. Between the bones is synovial fluid, preventing the bones from actually coming into contact with each other, and acting as a sponge to absorb the pressure of movement – it can be squeezed and squashed when the force of landing over a jump goes up the leg, without causing damage to the bones. The whole joint is surrounded by connective tissue and ligaments to give it strength and control the movement.
Osteoarthritis is a major cause of lameness in working horses. This is a disease which results in damage of the cartilage, causing inflammation, swelling, reduced mobility and pain. Certain horses are more prone than others:
- Young horses with immature joints in hard work (eg flat racing)
- Poor conformation puts extra pressure on certain joints
- Poor shoeing and foot balance can cause unlevel weight bearing
- Overweight horses put more stress on their legs
- Unfit horses asked to work harder than they are able
- Regular work on uneven or hard ground will increase the concussive forces on the joints.
Veteran horses may simply be suffering from the result of wear and tear over the years. As the body ages and becomes less able to repair the symptoms will reveal themselves. As the horse works, the joint is constantly being worn. As the tissues are being damaged, free radicals are created. The body’s own repair mechanisms are able to cope with this. Internal anti-oxidants help to mop up the free radicals before they accumulate and the chondrocytes set to work.
However, if this wear and tear builds up to a point where the chondrocytes cannot keep up, the free radicals will accumulate and further damage will be done. Affected joints will develop inflammation of the synovial membrane (synovitis), the articular cartilage will thin, the joints will then start to rub against each other, resulting in erosion of the joint surface. At this point there may be few visible symptoms. Perhaps the horse will be reluctant to extend his strides, there may be a change in temperament as a result of pain, he may become stiff on one rein, or just not perform to his usual standard. Continuing to work the horse will cause more erosion; the joints become less slippery, ultimately leading to further inflammation resulting in stiff movement, lameness and pain. As soon as a change in your horse’s performance and / or movement is noticed, the horse should be rested to slow the rate of joint erosion.
A Veterinary surgeon should also be consulted to make a diagnosis. The most common treatment involves anti-inflammatory and pain relieving drugs. Some may recommend injections directly into the joint, but the most common long-term treatment is Phenylbutazone. The side effects of drugs are well known, phenylbutazone may cause liver damage with regular use. However, recent research has also demonstrated that phenylbutazone causes further deterioration of the joint – the very area you are trying to help!
Glucosamine & Chondroitin sulphate
Chondroitin sulphate forms an important part of the structure of proteoglycans within the cartilage, but is also believed responsible for hindering the action of enzymes that cause cartilage degradation, and has anti-inflammatory properties. There is a question over the ability of the gut to absorb chondroitin as it is a large molecule, but preliminary studies have shown this to be a useful nutraceutical. Like glucosamine there are many grades available to the horse owner and it is important to choose a low molecular weight chondroitin (to increase the absorption rate) with 90% purity. Glucosamine and chondroitin work to support the synovial fluid and cartilage, but do not have enough anti-oxidant capacity of their own to reverse the harmful effect of free radicals. Anti-oxidants are an important part of everyone’s diet. They are found in fresh fruit and vegetables but they are easily destroyed. For a horse on box rest, fed only hay and hard feed, it is vital to supply anti-oxidants in the diet. Each anti-oxidant has its own properties, for example, vitamin A is good for eye health, and we have all been recommended to take vitamin C when we have a cold. Certain anti-oxidants are also recognised for their support during joint degeneration. Proanthocyanadins are a specific type of antioxidant found in berries and nuts. They are reported to be many times more efficient at removing free radicals than either vitamin C or vitamin E. In human health they are recommended for heart health, but another major quality of these antioxidants is that they can prevent collagen destruction. During inflammation, proanthocyanidins will inhibit the breakdown of collagen, and actually help to make the collagen within joints stronger. MSM is also a useful addition to any joint supplement. MSM helps to support the blood circulation, helping to remove the harmful debris around eroding joints more quickly. By making blood vessels more permeable, it will also help to reduce inflammation, therefore returning the joint to its original flexibility. MSM is also a source of sulphur – a vital mineral for soft tissue repair, which will therefore support healthy tendons, ligament’s and connective tissue.