Stringhalt in horses: causes and approach

What exactly is stringhalt?

With stringhalt, a horse involuntarily and spasmodically pulls a hind leg upward toward the abdomen with each step, sometimes so high that the hoof touches the abdominal wall. This occurs due to uncontrolled muscle contractions in the thigh muscles, specifically the musculus tibialis cranialis. The horse has no control over this. The disorder is most noticeable at walk and when backing up, but is sometimes barely visible at trot. Stringhalt can occur in one leg (unilateral) or in both legs (bilateral). Bilateral forms sometimes resemble a 'bouncy' or hedgehog-like gait pattern and are generally more severe.

Two main forms: classic and pasture

There are two clearly distinguishable forms:

• Classic stringhalt: develops gradually and is often one-sided. The exact cause cannot always be identified, but nerve damage or scar tissue around the hock joint likely plays a role.
• Pasture stringhalt (Australian form): occurs suddenly in multiple horses simultaneously in the same pasture. This is linked to the ingestion of certain plants such as false dandelion (Hypochaeris radicata) or certain fungi that contain a neurotoxin.
• Pasture stringhalt often resolves on its own once horses are removed from the affected pasture, sometimes within a few weeks to months.
• Classic stringhalt responds less predictably to treatment and can become chronic.
• Both forms require veterinary assessment to determine the appropriate course of action.

How do you recognise the symptoms?

The main features you as an owner may notice are:

• Excessive lifting of one or both hind legs at walk
• The leg 'shoots' up involuntarily, sometimes multiple times per step
• Symptoms often worsen in cold weather, with stress, or after rest
• Backing up is generally the most difficult and most noticeably affected movement
• At trot or canter, symptoms may temporarily be less obvious

Diagnosis and examination by the vet

There is no single blood test or imaging technique that confirms stringhalt. The diagnosis is clinical: the vet assesses movement at walk, when backing up, and possibly after a flexion test. Additional examination such as X-rays of the hock joint or an EMG (electromyography) can help rule out other conditions or assess the severity. Note in advance how long the symptoms have been present, which pasture the horse was on, and whether other horses show similar symptoms. This is enormously helpful to the vet. You can also record these kinds of observations in the horse profile in EquiSight, so you don't forget anything during the consultation.

Treatment options at a glance

• Pasture management: in cases of pasture stringhalt, remove immediately from the affected pasture and provide ample bedding
• Nutritional supplementation: vitamin E and selenium are sometimes used to support nerve tissue, in consultation with the vet
• Physiotherapy and exercise: light, controlled exercise helps some horses improve muscle coordination
• Medication: phenytoin (an anti-epileptic drug) has been used in severe cases, with variable results
• Surgery: in persistent classic stringhalt, a tenectomy (removal of part of the lateral extensor tendon) can offer a solution; recovery chances after surgery are around 60–70%

Prognosis and what to expect

The prognosis varies greatly depending on the form. Horses with pasture stringhalt recover fully in many cases within three to six months, provided they are removed from the pasture in time. With classic stringhalt the picture is more nuanced: mild cases sometimes remain stable and rideable, while severe cases deteriorate despite treatment. Regular monitoring is essential. Use the calendar in EquiSight to keep track of veterinary check-ups and physiotherapy appointments, and save video footage in the dossier so you can objectively compare progress or deterioration. This way you and your treatment team can stay on top of the situation.