Leg defences When a knight was fighting on a horse, the legs made a good target for the foot soldiers. Knights rarely wore leg armor because it made it difficult for them to walk. It was not until the twelfth century when some of them began to wear strip of mail armor on the front part of the legs. A heavy blow at the kneecap could cripple a knight for his entire life, so when plate armor was developed, the knee was the first area to be protected. By the forteenth century, most of the leg was covered in plate armor. Various other materials such as hard leather, whalebone or horns were often used instead of steel.