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 can involve one or both hind legs of the horse. It is a spasmodic contraction of the lateral extensor tendons of the hind legs.
There are four forms of stringhalt:Australian stringhalt: a flatweed (Hypochaeris radicata) is the suspected cause Pseudostringhalt: the apparent result of a painful condition in the affected leg Unilateral stringhalt: cause unknown, but often relieved by section of the lateral extensor tendon Bilateral stringhalt: in two out of two affected horses necropsied, abnormal thalamus