Until now, the methods used to set up in vitro gait simulations were not specimen specific, inflicting several problems when dealing with specimens of considerably different dimensions and requiring arbitrary parameter tuning of the control variables. We constructed a model that accounts for the geometric dimensions of the specimen and is able to predict the tibial kinematics during the stance phase. The model predicts tibial kinematics of in vivo subjects with very good accuracy. Furthermore, if used in in vitro gait simulation studies, it is able to recreate physiological vertical ground reaction forces. By using this methodology, in vitro studies can be performed by taking the specimen variability into account, avoiding pitfalls with specimens of different dimensions.