1. A method of preoperatively planning an arthroplasty procedure in a computer environment, the method comprising: a) access in the computer environment a first set of two dimensional medical images and a second set of two dimensional medical images, the first and second set of two dimensional medical images being the result of separate medical imaging events, wherein the first set of two dimensional medical images includes a plurality of anatomical landmarks and the second set of two dimensional medical images also includes the plurality of anatomical landmarks; b) locate first coordinate system points in the computer environment, the first coordinate system points approximating a knee center and at least one of a hip center or an ankle center, the locating of the first coordinate system points including an analysis of coronal two dimensional images of the first set of two dimensional medical images; c) define in the computer environment a mechanical axis between the knee center and at least one of the hip center or the ankle center; d) locate in the computer environment first landmark references and second landmark references, the first landmark references locationally approximating the plurality of anatomical landmarks in the first set of two dimensional medical images, and the second landmark references locationally approximating the plurality of anatomical landmarks in the second set of two dimensional medical images; e) computer generate a three dimensional knee computer model from the second set of two dimensional medical images; and f) applying via computer processing a transformation process to the first and second landmark references to cause the three dimensional knee computer model and at least one of the defined mechanical axis or the first coordinate system points to be positioned relative to each other in a global coordinate system of the computer environment generally as if the three dimensional knee computer model were generated from the first set of two dimensional images.