1. A method of preoperatively planning an arthroplasty procedure in a computer environment, the method comprising: a) access in the computer environment and via a network connection linked with a medical imaging system a first set of two dimensional medical images and a second set of two dimensional medical images, the first set of two dimensional images including a knee and at least one of a hip or ankle, the second set of two dimensional images including the knee, the first and second set of two dimensional medical images generated by the medical imaging system and 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 in the first set of two dimensional medical images; 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) positionally matching the first and second landmark references so as 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 correlated relative to each other with respect to position and orientation in a global coordinate system of the computer environment.