The aim of this final degree project is to study and analyze the kinematics of the human body lower limbs. First of all, it is extremely important to establish a protocol in order to compare two patients operated with two different techniques of total hip arthroplasty. The three usual movements that are employed to make this comparison are gait, sit-to-stand and stairs climbing. A three-dimensional full body model is implemented and the kinematic parameters (angles) necessary for the study are obtained by means of motion kinematic analysis techniques. Therefore, OpenSim software has been used to analyze the model. OpenSim is suitable to create a model with a multibody system of rigid bodies. This model has some markers attached to these bodies. By using Motive, it is possible to exchange information from a real subject to this multibody model. A Python program has been applied to synchronize both softwares and finally a Matlab code has been used to synchronize force plates with Motive. Finally, the results obtained have been analyzed and represented in graphics by applying OpenSim again. For this study, it has been necessary to use software and hardware at the UPC Biomechanics Laboratory. This project will also be developed in co-operation with clinical staff from the Traumatology Service of Hospital Universitari Vall d’Hebrón. It will be developed a protocol applied in a healthy person, then this study will be used in patient collaborating with the hospital.