The invention relates to a method and a device for determining an incorrect positioning in the alignment of prostheses for the lower extremities, said method comprising the following steps: determining inertial measurement data and/or variables derived therefrom by means of at least one inertial sensor, over at least one walking cycle, for an extremity provided with a prosthesis; and comparing the inertial measurement data that has been determined and/or the variables derived therefrom with desired values and/or with measurement data that has been determined or variables derived therefrom for the corresponding extremity that is not provided with the prosthesis.