Stringhalt in Horses: Causes, Symptoms, Treatment, and Management

Stringhalt is a neuromuscular condition in horses characterised by an exaggerated, involuntary flexion of one or both hind limbs. Horses affected by stringhalt lift the hind leg sharply and abruptly toward the abdomen during movement, especially when walking or turning. The condition can range from mild and intermittent to severe enough to interfere with normal movement and performance.

Although stringhalt is often alarming to observe, its causes, progression, and prognosis vary depending on the type of stringhalt involved. Understanding the condition can help horse owners recognise the signs early and make informed decisions about treatment and management.

What Is Stringhalt

Stringhalt is a neurological gait abnormality affecting the hind limbs of horses. It is primarily associated with dysfunction of the nerves that control the muscles responsible for flexing the hind leg.

When a horse with stringhalt moves, the hind leg may snap upward suddenly in an exaggerated flexion before returning quickly to the ground. This abnormal motion is most noticeable during slow movement, such as walking or turning sharply.

The condition can affect:

• One hind leg (unilateral stringhalt)
• Both hind legs (bilateral stringhalt)

Severity varies widely. Some horses only show subtle abnormalities during certain movements, while others may struggle to walk normally.

Types of Stringhalt

There are two main forms of stringhalt in horses: classic stringhalt and Australian stringhalt. Although they appear similar, they differ significantly in cause and progression.

Classic Stringhalt

Classic stringhalt typically affects only one hind leg and is usually sporadic. It is believed to involve damage or dysfunction of the long digital extensor nerve, which controls muscles responsible for extending the lower limb.

Classic stringhalt:

• Usually affects a single limb
• Often develops gradually
• May follow trauma, nerve injury, or inflammation
• Can remain stable or slowly worsen over time

The exact cause is not always identifiable.

Australian Stringhalt

Australian stringhalt is a pasture-associated condition that affects multiple horses in the same area. It is most commonly reported in Australia and New Zealand but has also been documented in the United Kingdom, Europe, and North America.

This form of stringhalt is believed to be caused by toxins from certain pasture weeds, most notably Hypochaeris radicata (commonly known as flatweed or cat's ear).

Characteristics of Australian stringhalt include:

• Often affects both hind limbs
• Multiple horses on the same pasture may be affected
• Signs may appear suddenly
• Severity can vary widely between horses

Unlike classic stringhalt, Australian stringhalt may improve or resolve once horses are removed from contaminated pasture.

Causes of Stringhalt

The underlying cause of stringhalt involves disruption to the nerves controlling hind limb movement. The exact mechanism varies depending on the type of stringhalt.

Possible Causes

Classic stringhalt

• Nerve damage affecting the long digital extensor nerve
• Trauma to the hind limb
• Inflammation or scarring around nerves
• Previous surgery or injury to the limb
• Unknown neurological dysfunction

Australian stringhalt

• Grazing on pastures containing toxic plants, particularly Hypochaeris radicata
• Exposure to plant toxins that damage peripheral nerves
• Nutritional deficiencies associated with poor pasture conditions
• Environmental stressors during drought conditions

Pasture-associated outbreaks often occur during dry seasons when desirable forage is scarce and horses graze more heavily on weeds.

Symptoms of Stringhalt in Horses

The hallmark sign of stringhalt is exaggerated flexion of the hind limb during movement. However, the severity and presentation can vary considerably.

Common Clinical Signs

• Sudden, exaggerated upward flexion of the hind leg
• Jerky or snapping movement during walking
• Abnormal gait when turning or backing up
• Difficulty moving backwards
• Occasional stumbling or loss of coordination
• More pronounced symptoms during excitement or cold weather

Some horses show signs only intermittently, particularly when first moving after rest.

Severe Cases

In severe forms, particularly Australian stringhalt, horses may show additional signs:

• Both hind legs snapping upward dramatically
• Difficulty walking normally
• Muscle wasting in the hindquarters
• Reluctance to move
• Abnormal posture when standing

In extreme cases, the leg may lift so high that the hoof strikes the abdomen.

Diagnosis

Diagnosis of stringhalt is primarily based on clinical observation of the horse's gait. A veterinarian will evaluate the horse moving in different conditions to assess the characteristic hind limb movement.

Veterinary Examination

A thorough examination typically includes:

• Observation of the horse walking and turning
• Assessment of hind limb flexion and coordination
• Neurological examination
• Evaluation for other causes of hind limb lameness

Because several neurological or musculoskeletal conditions can mimic stringhalt, further testing may sometimes be required.

Differential Diagnoses

Conditions that may resemble stringhalt include:

• Shivers
• Upward fixation of the patella
• Fibrotic myopathy
• Equine protozoal myeloencephalitis (in some regions)
• Other neurological disorders affecting gait

Accurate diagnosis is important to determine the most appropriate treatment approach.

Treatment

Treatment options depend on the severity and underlying cause of stringhalt. Some mild cases require little intervention, while more severe cases may benefit from surgical or medical management.

1. Pasture Management

For horses suspected of having Australian stringhalt, the most important first step is removing them from the affected pasture.

Management strategies include:

• Moving horses to weed-free pasture or dry lots
• Improving pasture quality
• Removing toxic plants such as flatweed
• Providing adequate forage and nutrition

Many horses show gradual improvement once exposure to the suspected toxin is eliminated.

2. Medical Therapy

Medical treatment may include supportive therapies aimed at improving nerve function.

Common options include:

• Vitamin E supplementation to support nerve health
• B-complex vitamins
• Anti-inflammatory medications if inflammation is suspected
• Physiotherapy or controlled exercise

Scientific evidence for medical treatments varies, but nutritional support is commonly recommended.

3. Surgical Treatment

In cases of classic stringhalt that do not respond to conservative management, surgery may be considered.

The most common procedure is lateral digital extensor tenectomy, which involves removing a section of the tendon responsible for the exaggerated flexion.

Potential outcomes include:

• Reduced severity of abnormal movement
• Improved gait and comfort
• Return to athletic activity in some horses

Recovery time following surgery typically involves several weeks of rest and controlled exercise.

Management and Rehabilitation

Long-term management focuses on maintaining mobility, improving nerve function, and preventing worsening symptoms.

Exercise Management

Controlled exercise can help maintain muscle strength and coordination.

Recommended approaches include:

• Regular turnout
• Light riding or groundwork if the horse is comfortable
• Avoiding abrupt turns or stressful work

Horses with mild stringhalt may continue normal exercise routines.

Nutritional Support

Nutrition plays an important role in nerve health.

Common recommendations include:

• Vitamin E supplementation
• Balanced mineral intake
• High-quality forage

Consulting an equine nutritionist or veterinarian can help ensure appropriate supplementation.

Monitoring

Owners should monitor affected horses for changes in:

• Gait severity
• Muscle development
• Comfort during movement

Any sudden worsening should be evaluated by a veterinarian.

Prognosis

The outlook for horses with stringhalt depends largely on the type and severity of the condition.

Classic Stringhalt

• Mild cases may remain stable for years
• Surgical treatment often improves gait abnormalities
• Some horses return to full athletic performance

Australian Stringhalt

• Many horses improve once removed from toxic pasture
• Recovery may take several months
• Severe cases may have lasting neurological deficits

Early intervention and proper management improve the likelihood of recovery.

Prevention

Preventive measures focus primarily on pasture management and early recognition.

Pasture Control

• Regularly inspect fields for toxic weeds such as flatweed
• Maintain healthy pasture through proper grazing management
• Avoid overgrazing during drought conditions
• Provide supplementary forage when pasture quality declines

Good Stable Management

• Ensure horses receive balanced nutrition
• Monitor horses for abnormal gait changes
• Rotate grazing areas to reduce weed dominance

Early detection of abnormal hind limb movement allows prompt veterinary evaluation and management.

When to Contact a Veterinarian

Horse owners should seek veterinary advice if they notice:

• Sudden exaggerated hind limb movement
• Difficulty walking or backing up
• Rapid progression of gait abnormalities
• Multiple horses on the same pasture showing similar symptoms

Prompt evaluation helps rule out other neurological or orthopaedic conditions and ensures appropriate treatment.

Conclusion

Stringhalt is a distinctive neurological condition that causes exaggerated hind limb flexion in horses. While the abnormal movement can be striking, the severity and long-term impact vary widely depending on the underlying cause.

Classic stringhalt often affects a single limb and may respond well to surgical treatment, while pasture-associated Australian stringhalt can affect multiple horses and may improve once toxic plants are removed from the environment.

With careful observation, veterinary guidance, and proper pasture and nutritional management, many horses with stringhalt can maintain good quality of life and, in some cases, return to normal work.