Stringhalt is a sudden flexion of one or both hind legs in the horse, most easily seen while the horse is walking or trotting. It is most evident when the horse is backing up slowly, turning on the affected leg, or suddenly frightened. It involves one or both hind limbs of the horse. It is a spasmodic contraction of the lateral extensor tendons of the hind legs.

There are 4 forms of stringhalt:
Butler

1. Australian stringhalt: a false dandelion (catsear
   Catsear
   Catsear , also known as flatweed, cat's ear or false dandelion, is a perennial, low-lying edible herb often found in lawns. The plant is native to Europe, but has also been introduced to the Americas, Japan, Australia and New Zealand where it can be an invasive weed...
   
   ) is the suspected cause
2. Pseudostringhalt: the apparent result of a painful condition in the affected leg
3. Unilateral stringhalt: cause unknown, but often relieved by section of the lateral extensor tendon
4. Bilateral stringhalt: in two out of two affected horses necropsied, abnormal thalamus
   Thalamus
   The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
   
   

Treatment varies.

See also

• Scotty cramp
  Scotty Cramp
  Scotty Cramp is a disease in Scottish Terriers causing spasms and hyperflexion and hyperextension of the legs. It is caused by a disorder in serotonin metabolism that causes a deficiency of available serotonin. It is inherited as an autosomal recessive trait....
  
  a condition in dogs that may resemble stringhalt in horses