A mobile measuring system was developed to study the mobility and activity of amputees with focus on the applied loads to the metallic structures and therefore the resulting loads to the prosthesis. Equipped with strain gauges, the system had to be applicable to prosthetic adapters and meet certain criteria like limited geometrical - and strength - requirements. The developed portable system is able to record data (3D forces and moments) throughout the daily use of a prosthesis. First results were obtained in a study on transtibial amputees which were then used for the development of testing procedures for knee braces. With the results of an ongoing study on 15 transfemoral amputees over a period of one year a database can be generated to re-evaluate parameters of international standard testing (ISO 10328). Furthermore potentials for safer prostheses and higher functionality can be deduced from this data.