Nowadays, the simulation software in biomechanics have a fundamental role in the analysis and the study of the human body’s dynamics. Opensim is one of the most important in this field of study. This open-source software system lets users develop and simulate a large variety of musculoskeletal model and create different movements of these models. In Opensim a model is a codified description of the form and function of a biomechanical system, which can include neural, muscular and skeletal structures, as well as artificial components like exoskeletons. These new robotic systems are increasingly in contact with human body and represent the most important examples of human-oriented robotic devices.