In this paper we present a human-oriented approach to the study of the biped gait for a humanoid robot. Starting from the analysis of the human lower-limbs, we figured out which features of the human legs are fundamental for a correct walking motion and can be adopted in the mechanical design of a humanoid robot. In particular we focus here on the knee, designed as a compliant human-like knee instead of a classical pin-joint. For the foot we tried to reproduce in a simple mechanical device the mobility and lightness of the human foot, which is very different from a flat surface and has a big impact on walking. We complete the presentation with considerations about the energy consumption of our humanoid design. In our approach the robot gains in adaptability and energetic efficiency, which are the most challenging issues for a biped robot.