Sidewinder Syndrome in Horses

What is sidewinder syndrome?

Sidewinder syndrome, also known as side walker or crab walker, describes a gait in which the horse’s hind limbs and pelvis drift to one side, while the front limbs track normally. It often comes on suddenly but can also appear gradually. Horses may have difficulty standing still. In severe cases, they may spin or circle in place. Some affected horses lean on a wall, fence, or stocks for support. Older horses are more commonly affected than younger horses. The mean age in a study of 24 affected horses was 19 years old (Aleman et al. 2020). Sidewinder gait can affect horses of any breed and sex.

What causes sidewinder syndrome?

Sidewinder syndrome is not well understood and has various causes, including musculoskeletal, neurologic, or a combination of conditions. Neurological causes include compression of the spinal cord, spinal cord damage, and equine protozoal myeloencephalitis (EPM). Musculoskeletal causes include osteoarthritis of the hip joint, pelvic fractures, and hip ligament rupture.

Diagnosis of the underlying cause can be challenging since horses are unstable and sedation that may be needed for certain diagnostics can exacerbate behaviors such as excessive leaning and spinning.

How is sidewinder syndrome diagnosed?

Diagnosis of the underlying condition causing sidewinder gait can involve a physical examination, neurological examination, and diagnostic tests such as blood tests and imaging. Electromyography, which records electrical activity in muscle, may be used to identify neurologic versus non-neurologic diseases.

How is sidewinder syndrome treated?

Sidewinder gait is treated by managing the underlying cause. This can include antiprotozoal medications for EPM, anti-inflammatory drugs, and antioxidants (including vitamin E).

What is the prognosis for sidewinder syndrome?

The prognosis for full recovery for horses that exhibit sidewinder gait is generally poor but varies depending on the underlying cause. Some horses are pasture sound, but the underlying condition often continues to progress over time.

How can sidewinder syndrome be prevented?

Since there are so many possible underlying causes, it is challenging to prevent sidewinder syndrome. If you notice a horse exhibiting sidewinder gait, contact a veterinarian immediately.

For more information

Aleman, M., Berryhill, E., Woolard, K. et al. Sidewinder gait in horses. JVIM 2020;34:2122-2131.