Q: I work at a fairly large equine facility and have seen many horses come and go through the years. However, a few months ago a Quarter Horse mare here developed a condition I’d never seen before, known as sidewinding. She can still walk, but not straight. When put on a longe line, she moves like she is in a constant shoulder-in. Many veterinarians have been out to the farm but none of them know what has caused it or how to cure it. One recommended a particular supplement, and within a month the horse got a little better, but she still can’t walk straight and always has a slight bend to the right. Can you tell me more about this?
A: This is indeed an interesting case. “Sidewinding” is not a specific syndrome but instead just a description of the horse’s way of traveling---in this case, with a constant slight bend to the right. There are several potential reasons why the mare might move like this. The cause could be either neurological or orthopedic or maybe even some combination of both. Here are just a few possibilities:
• Diseases of the central nervous system (that is, those that affect the brain and/or spinal cord) can alter the way the brain sends messages to the muscles. Two examples are equine protozoal myeloencephalitis (EPM) and West Nile encephalitis.
• Injuries to the spinal column can impinge on the nerves that control the muscles. For example, I have seen horses sustain severe injuries to the neck which left them fully functional but unable to move as they once did. Also, Wobbler’s syndrome, which stems from a malformation of the neck vertebrae that presses on the spinal cord, could cause the sidewinding to develop. Arthritic changes in the neck vertebrae can have the same effect.
• Infections in the middle ear can alter the horse’s balance and cause abnormal gaits. As you can see, it may require a very extensive examination to determine the cause of this mare’s abnormal gait. It would be a good idea to avoid riding her until it can be proven that she is safe and not likely to fall.
On a personal note, one of my own horses is a 10-year-old Quarter Horse gelding who has had a sidewinding gait since I got him at a few months of age. I have not been able to find the origin of his sideways way of going. He had a serious hock injury as a foal but has never been lame as an adult. I have won money team penning and ranch sorting on this horse, but it drives my wife (who is an upper-level dressage rider) crazy to ride him.
Bruce A. Connally, DVM, MS Wyoming Equine Longmont, Colorado
This article first appeared in EQUUS issue #440.