Neurologic or musculoskeletal origins identified in cases of sidewinder gait in horses

Clinical presentation of sidewinder gait in terms of body posture. Both horses were classified as having neurologic disease.
Clinical presentation of sidewinder gait in terms of body posture. Both horses were classified as having neurologic disease.

Several neurologic or musculoskeletal causes were linked to sidewinder gait in horses in a retrospective study of cases at two veterinary institutions.

Sidewinder gait in horses is poorly understood and characterized by walking with the trunk and pelvic limbs drifting to one side.

In severe cases, horses spin or circle in one place with their pelvic limbs moving in one direction while the thoracic limbs move in a compensatory manner.

Investigation of the distressing condition, with affected horses, sometimes referred to as side walkers or crab walkers, is challenging, as they can have difficulties standing in one place, or to stand symmetrically loading their pelvic limbs.

Researchers with the University of California, Davis, and the now-closed Animal Health Trust in Britain hypothesized that the gait might have causes that range from musculoskeletal, neurological, to a combination of conditions.

Onset can be sudden or insidious, such as being awkward about picking up their feet for farrier work.

For their study, Monica Aleman and her colleagues set about describing the clinical and neurological findings, diagnostic results, and outcome of horses with sidewinder gait presented to two referral institutions.

The cases were seen at either the William R. Pritchard Veterinary Medical Teaching Hospital at the University of California, Davis, or the Centre for Equine Studies at the Animal Health Trust in Newmarket, England, between 2000 and 2019.

Thirty‐seven horses with sidewinder gait were identified but 13 were excluded because of incomplete clinical information, no diagnostic workup, or the lack of a postmortem examination.

Clinical presentation in terms of musculature. Note the musculature of the pelvic area and pelvic limbs in 2 horses with acute onset of sidewinder gait. Images were taken weeks after onset. Horses A and B had neurologic disease; C had musculoskeletal disease.

Twenty‐four horses were included in the study — 18 cases from the hospital in California, four from the Animal Health Trust, and two from external consulting.

The average age of the horses, of various breeds, was 18.9.

Onset was acute in 10 of the cases, subacute in six, and insidious in eight.

Neurologic origins were identified in 16 cases.

Neurologic causes included dynamic thoracolumbar spinal cord compression in five cases, equine protozoal myeloencephalitis in four cases (two confirmed and two presumed), thoracic myelopathy of unknown cause in four cases, two cases involving gliosis, and one case involving thrombosis of thoracic spinal cord segments.

Electromyography (an electrodiagnostic technique for evaluating and recording electrical activity produced by muscles) and muscle biopsy supported the finding of neurologic disease in nine cases, with the source of the lesion successfully localised.

Non‐neurologic causes were found in eight cases: Osteoarthritis of the coxofemoral joint in four cases, multiple displaced pelvic fractures in two cases, bilateral rupture of the ligamentum capitis ossis femoris in one case, and severe myonecrosis of multiple pelvic limb muscles in another.

Treatment in these horses was mainly supportive and palliative to address possible pain and inflammation, oxidative damage, and in some cases the use of antiprotozoal medication for those horses with presumed equine protozoal myeloencephalitis.

“Although short‐term improvement was observed with therapy, the sidewinder gait remained unresolved,” the study team reported in the Journal of Veterinary Internal Medicine.

The fatality rate among the horses in the study was 79% (19 of 24).

“Resuming previous physical activity was not achieved in the remaining live horses and long‐term follow‐up in two horses out in pasture revealed a persistent sidewinder gait.”

The study team concluded that sidewinder gait is usually observed in older horses of any breed and sex, and can have neurologic or musculoskeletal origins.

“Electromyography can be used as a diagnostic aid to determine neurologic versus non‐neurologic disease and further localize those of neurologic origin.”

The condition often has a poor prognosis for function and life, they said.

The study team comprised Aleman, Emily Berryhill, Kevin Woolard, Charlotte Easton‐Jones, Tania Kozikowski‐Nicholas and Isabelle Kilcoyne, all with the University of California, Davis; and Sue Dyson, with the Animal Health Trust during the period the case reviews covered.

Sidewinder gait in horses. Monica Aleman, Emily Berryhill, Kevin Woolard, Charlotte A. Easton‐Jones, Tania Kozikowski‐Nicholas, Sue Dyson, Isabelle Kilcoyne.
Journal of Veterinary Internal Medicine, August 21, 2020,

The study, published under a Creative Commons License, can be read here

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