Striking with the front feet is usually an aggressive or defensive behavior directed at a perceived threat or it happens in the presence of another horse. It is a natural herd behavior and is common in both stallions and mares.

However, when solitary horses strike out with the forelimbs for no apparent reason it can indicate painful or irritating conditions affecting the face, mouth or head.

In rare cases, horses with specific brain conditions, injuries or illnesses can spontaneously and randomly strike at no apparent target. If all other causes are ruled out, there is a rare psychologic disorder in which horses can show this behavior, often along with biting at the sides, limbs or chest.

Striking can also be directed at people. Certain untrained or poorly trained horses may strike when they feel cornered, threatened or pressured. Striking behavior can be worsened by excessive downward pressure on the face with a halter. Horses that have not been trained to yield to pressure are more likely to engage in this behavior. Some horses will strike violently when they are being twitched.

Regardless of the underlying cause, striking is a very dangerous and an undesirable behavior. Handlers standing in front of a striking horse can be severely injured. It can be hard to predict when a horse will strike.