An employee climbed onto the platform of a K-loader from the back of a unit load device (ULD). The employee was walking on the platform when it began ascending. The operator of the K-loader stopped the platform when they saw the employee come out from the back of the ULD. The employee then took a step and fell from the platform to the ground, sustaining fractures to the tibia and fibula of his left leg and a fracture to his right leg.