A method for calculating the location of the center-of-rotation of a joint with an attached member. The method employs an inertial measurement unit (IMU) having an angular rate gyro and an accelerometer and coupling the inertial measurement unit to the member for detection of movement of the member. The inertial measurement unit outputs data representative of angular velocity and acceleration of the member mounted IMU in response to movement of the joint. The method further comprising analyzing the angular rate and acceleration data to determine the center-of-rotation of the joint.