How to Identify and Manage Stringhalt in Dressage Horses ⋆ How To Dressage

If you’re a dressage rider, you’ll know the importance of regularity in the horse’s paces.

Take a look at the Scales of Training, and you’ll see that “rhythm” is the first of the scales, and it is also the most important.

If the horse does not work in a regular rhythm, or if the sequence of footfalls in any of the paces is incorrect, the judge has no choice but to give a poor mark for each movement where irregularity is present. Also, the collective mark for the horse’s paces will be negatively affected.

So, if a horse has stringhalt, can you still be successful in the dressage arena?

Let’s find out.

What is stringhalt?

Stringhalt is a gait abnormality in horses that manifests itself as an exaggerated, abrupt flexion of one or both hind limbs.

Stringhalt occurs when the horse’s digital flexor muscles have insufficient opposition or when the digital extensor muscles contract to excess.

Both the horse’s hind legs can be equally affected. However, one or more hind leg can be more obviously affected than the other.

Other signs of the disease include shivering or foreleg stringhalt.

What causes stringhalt?

At first glance, stringhalt appears to be a muscular problem. However, neurological issues are the real cause of the condition.

Nerve damage likely affects the activity of sensory receptors called spindles. Spindles are found in the body of the muscles and are responsible for interpreting changes in muscle length.

The spindles’ “faulty wiring” can cause particular muscles to contract either too late or too early, too little or too much.

There are two recognized forms of stringhalt:

Australian stringhalt

Veterinarians first identified the condition in Victoria, Australia in the late 19^th century. However, the disease affects horses worldwide and is relatively common in the U.S. and New Zealand, as well as Australia. Also, the condition has recently been seen in some South American countries.

Australian stringhalt attacks the horse’s peripheral nervous system, usually affecting both hind legs equally and sometimes the forelegs too.

Sometimes, the horse’s larynx is affected, causing a hoarse roar when the horse tries to whinny. In some animals, the restriction to the horse’s airway can be permanent, causing permanent problems with athletic performance.

Australian stringhalt affects grass-kept horses and is thought to be caused by the ingestion of toxic plants, in particular by the consumption of the noxious weed, Hypochoerris radicata, commonly called “flatweed.”

Horses are typically affected by the condition in the late summer or fall if grazing on very weedy pastures.

However, in some cases, horses can graze in paddocks that contain potentially toxic weeds and remain unaffected. It’s thought that the locale and environment can play a role in providing the perfect conditions for toxins to be produced by the plants.

As soon as the clinical signs of Australian stringhalt are seen, the horses should be removed from their pasture.

Most horses recover within six to nine months, although in some cases the median recovery period can be as little as a few weeks or as long as several years.

Classic stringhalt

The classic form of stringhalt affects only one rear limb.

The limb jerks suddenly upward in spasm toward the horse’s belly, generally when the horse is asked to move.

The effect of stringhalt varies. Sometimes the action may be violent and exaggerated or mild and barely noticeable.

The cause of classic stringhalt is not known. However, injury to the horse’s neck, back, or leg can be the underlying cause of the condition. In such cases, once the injury has healed, the condition usually improves. Sometimes, degenerative joint disease, osteochondritis dissecans (a condition affecting the cartilage in the horse’s neck joints) could be the cause.

Studies have shown that the clinical signs of the condition progress as the horse gets older, often from the age of three to five years.

In dressage horses, that’s the optimum age for more complex gymnastic exercises to commence, so it’s not known if the stringhalt advances because of training or the horse’s age or both.

Unlike the self-resolving Australian stringhalt, classic stringhalt does not usually resolve and remains persistent throughout the horse’s lifetime.

When does stringhalt occur?

Stringhalt is usually triggered when the horse is asked to move, typically when the horse is asked to back up or turn around. For example, when the horse is led out of his stable or when the horse is asked to rein-back after a prolonged halt.

Sometimes, stringhalt can be triggered by excitement.

In very mild cases, the limb flexion is so minor that the gaits above the walk appear normal.

When it ISN’T stringhalt

Some conditions may be mistaken for stringhalt.

For example, rear foot pain such as from an abscess can present with the same symptoms as stringhalt. Also, pain from the stifle or hock joint can cause a horse to jerk his limb upward abruptly.

Other conditions that can cause stringhalt-like symptoms can include:

Upward fixation of the patella
Fibrotic myopathy
Shivers
Equine protozoal myeloencephalitis

Therefore, it’s vital that you have your vet carry out a thorough examination to make a definitive diagnosis.

Diagnosis

Horses with Australian stringhalt don’t require the same extensive diagnostic procedures as those with classic stringhalt because the cause of the condition is already known.

Animals with classic stringhalt should undergo a detailed orthopedic examination, including X-rays and ultrasound scans of the affected leg.

That will allow a specialist vet to detect any abnormalities that might cause abnormal reflexes in the horse’s lateral digital extensor muscle, hock, or tendon.

Also, the possibility of muscle diseases such as polysaccharide storage myopathy should be considered.

Stringhalt patients should be hospitalized for a few days to allow for multiple examinations, including an orthopedic workup, clinical exams, diagnostic imaging, and electromyography to measure the electric signals in the muscles.

Treatment

Stringhalt can be treated with anticonvulsants and other drugs that work directly on the horse’s central nervous system.

The downside of this form of drug therapy is that it can have a sedative effect, and the results are often temporary. Obviously, that makes drug treatment of this kind unsuitable for horses in competitive situations.

A surgical route is also possible where part of the tendon that runs along the hock is re-sectioned, but the success of this method varies.

Currently, use of the botulinum toxin, Botox, is being investigated and has shown positive results in calming stringhalt symptoms. The idea of the treatment is to help the horse to overcome the neurological issues that cause stringhalt. Although the idea may sound somewhat far-fetched, positive results are being seen in people with motor neuron disorders.

In conclusion

Stringhalt is a condition that affects the hind limbs, causing the horse to snatch the leg upwards towards his belly, usually when the horse is asked to move after a period of inactivity.

In dressage horses, stringhalt is usually most noticeable in the walk where the movement concerned is marked down for irregularity in the rhythm.

Do you have a horse with stringhalt? How has your horse’s condition affected your dressage career?

Share with us in the comments section below.

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