This paper presents the biomechanical model of a prosthetic leg. In order to study the change of speed in the joint prosthesisstump upon impact of the foot with the ground is modeled as a spring-damper system, allowing demonstrate the need to build the stump-prosthesis junction impedance devices mechanical variable. This platform is also proposed with the aim of simulating virtual representations to a patient with prosthesis, as a stage prior to the actual implementation thereof.