Stringhalt is a condition that can affect any breed or age of horse, which is not painful. It can be very simply diagnosed by the evident gait: an uncontrollable and exaggerated lifting of each hind leg, almost as if they were kicking their belly with their fetlocks. It can affect either one or both hind limbs. The severity of the action can depend on the horse, and sometimes shaking can also be seen.
Although it may look like a muscular or tendon injury, it is actually a neurologic problem. Like a faulty cable that can produce bad signal, damage to the neurons create this odd movement.
The causes of stringhalt can be divided into two categories: Australian, which has been found to be caused by a toxicity, and classic, which has no known cause and tends to not resolve on its own. Classic stringhalt also tends to affect one hind leg, and could be more likely due to injury. Australian stringhalt has been associated with horses ingesting Hypochaeris radicata, also known as "flatweed", which is a yellow flower which looks like a false dandelion.
Other causes include nutritional deficiencies (minerals, vitamins) and other plants or old forage and grains producing mycotoxins. Once ingested, these mycotoxins can cause neurological damage. Sometimes, horses can have outbreaks of stringhalt, where multiple horses are affected from the same grazing field. Removing the horses from infested pastures is usually the sole treatment, and stringhalt will then resolve spontaneously.
Horses with stringhalt should be examined by a veterinarian to rule out neurological disease or lameness. A short course of anti-inflammatories may be needed. But always be sure to check your fields for signs of toxic plants, or any fungi.