A computer-implemented method for determining changes in parameters of a hip joint due to modification of the hip joint comprises establishing a first position of a pre-operative center of rotation of the joint in a first coordinate space. The method further comprises estimating a second position of the pre-operative center of rotation of the joint in the first coordinate space, when the estimated pre-operative center of rotation is maintained in a constant position in a second coordinate space. A change in a parameter associated with the joint is determined based on the first and second positions of the pre-operative center of rotation of the joint.