If there was damage to the leg the pin-firing helps the ligiment heal faster and better. Every year hundreds of racehorses undergo a procedure called thermo-cauterisation - commonly known as pinfiring. It is a crude, painful leg operation that involves the insertion of red-hot needles through the skin to burn the damaged tendon or ligament. The purpose is to stimulate an inflammatory response around the injury and thereby enable a horse with damaged and bruised limbs to continue taking the knocks and bruises as they perform. Its also banned in the UK and ireland..