The EE was adding antifreeze to loader radiator on backside of loader. As he finished, he stepped down off platform onto top ladder rung. He was holding railing with his left, hand he stepped onto top rung with his right foot. As he then stepped down to the second rung with left foot, he had a misstep, lost his grip on railing and fell 2 feet 9 inches to the ground on his knees.