Disclosed herein is a method of computer generating a three-dimensional surface model of an arthroplasty target region of a bone forming a joint. The method may include: generating two-dimensional images of at least a portion of the bone; generating an open-loop contour line along the arthroplasty target region in at least some of the two-dimensional images; and generating the three-dimensional model of the arthroplasty target region from the open-loop contour lines.