Traditional stringhalt is a poorly understood condition in which the horse hyperflexes one or both hocks. It usually occurs in adult horses, is gradual in onset, and be slowly progressive. The majority of horses recover completely, but a few deteriorate progressively. The condition may be caused by ingestion of a plant toxin.
Signs
The horse exaggeratedly flexes one or both hind limbs when in motion. The abnormality is sometimes evident at all paces, but it is usually most apparent at walk, especially if the horse is turned or backed, and may disappear at trot. The condition may be intermittent and remain static or deteriorate.
Treatment
Most often, the cause of the condition is unknown. Some horses are successfully treated by the removal of a piece of the lateral digital extensor tendon at the level of the hock.
Prognosis
Unless the gait abnormality is extremely severe, affected horses are usually able to perform adequately, including jumping, but are unsuitable fro dressage. A guarded to fair prognosis is warranted after surgery. Some horses improve initially but subsequently relapse.
Sometimes stringhalt may develop a complication following trauma to the dorsal metatarsal region. Potential causes include tendon injury that result in abnormal flexion of the tarsocrural joint. Horses may develop stringhalt within 3 months after injury. They can be treated with exercise, including daily hand-walking with pasture turnout, followed by lunging; or surgically, using lateral digital extensor myotenectomy. Of the horses treated with exercise, some may have resolution of stringhalt. Horses treated surgically have varying degrees of improvement, or no change.
References:
1. Veterinary Notes for Horse Owners, Captain M.Horace Hayes, F.R.C.V.S.
2. Crabill MR, Honnas CM, Taylor DS, Schumacher J, Watkins JP, Snyder JR. (pubmed.gov)