An employee was working from a ladder to remove ductwork from the ceiling. He snipped a hanger on one end at the joint and the duct joint gave way, causing the ductwork to drop at one end and swing back, striking the ladder at the base. This knocked the ladder out from under him, and he fell to the floor, landing on his hands and knees at an angle. He broke his arm, fractured his elbow, and hurt his knee.