A shoe boil is a soft, flabby swelling caused by an irritation at the point of the elbow. This is where the name capped elbow came from. The two common causes of this unsoundness are injury from from heel calks on the shoe and injury from contact with the floor stall or laying on any hard surface. The horse may or may not go lame. It depends on the degree of inflammation and the size of the swelling. If discovered quickly the shoe boil may be successfully treated by daily applications of tincture of iodine and the use of a shoe boil boot
. These boots or boil rolls are placed around the pastern so that the heel is prevented from coming into contact with the elbow while the horse is lying down. In the worst cases surgery by a veterinarian may become necessary.