Marker based motion data of pre- and one year postoperative examinations on nine subjects who underwent reverse shoulder arthroplasty were analyzed applying functional methods for joint center estimation. The aim was to determine the location of the functional center of rotation in the operated and the non-operated contralateral side before and after surgery to verify if the joint center of this reverse prosthesis design is located more medially compared to the anatomic situation before surgery. It was shown that the operated shoulders demonstrated a medialization effect of 8.3 ¡À 4.3 mm. For the non-operated side the difference was 0.1 ¡À 2.3 mm, proving the accuracy of measurements.