In this paper, we present a method of simulating walking motions with leg disease using humanoid robots based on our optimal dynamic multi-contact motion generation technique. We take into account full-body dynamics model of the robot and consider additional physical constraints. We have run the generated motions with HRP-2 humanoid robot platform and identified extra energy consumption due to the constrained leg motions using an infra-red camera. This research is the first step towards the usage of humanoid robots for studies and diagnosis on humans' disabled motions as well as active mannequin for welfare instrument evaluation.