In this study, dynamic modeling of gait, which is useful in studies such as lower limb prosthetic design, two-legged robotic walking, is discussed with two degrees of freedom pendulum model. Using the Lagrangian Dynamics, non-linear dynamic equations of the gait, especially emphasized for the swing phase, were obtained in a nonlinear and coupled structure. Equations were derived from the modified dynamic expressions of a robot arm manipulator with two degrees of freedom. The performance of the proposed model was validated with forward and inverse solutions using gait database. The model obtained in this case was considered to be more complete with less simplification and unlike similar approaches the closed dynamic equations were defined in a more realistic framework without partial linearization and uncoupling. In this way, a more comprehensive and realistic model has been examined analytically. The appropriateness of the double pendulum model for the swing phase is presented both partially linearized model and authors' proposed model in this paper by forward and inverse solutions in this paper.