1. A method of manufacturing a custom arthroplasty resection guide, the method comprising: generate a three dimensional femur bone computer model from MRI knee coil two dimensional images, wherein the MRI knee coil two dimensional images include a knee region of a patient; locate positions of an approximate hip center and an approximate femur knee center in coronal view MRI body coil two dimensional images, wherein the positions are relative to at least two axes in a global coordinate system of a computer environment and wherein the MRI body coil two dimensional images include a hip region of the patient and the knee region of the patient; cause the three dimensional femur bone computer model and approximate hip center and approximate femur knee center to generally correspond with each other with respect to location and orientation in the global coordinate system of the computer environment by aligning first locations of knee landmarks in the MRI knee coil two dimensional images and second locations of the knee landmarks in the MRI body coil two dimensional images; define across the three dimensional femur bone computer model a femoral mechanical axis between the approximate femur knee center and the approximate hip center; locate a most distal condylar point of the three dimensional femur bone computer model; define a distal plane that is orthogonal to the femoral mechanical axis in a coronal view of the three dimensional femur bone computer model, wherein the distal plane also passes through the most distal condylar point; define a resection plane that is parallel to the distal plane and proximally offset a distance along the femoral mechanical axis from the distal plane; and manufacture the custom arthroplasty resection guide by using data associated with the resection plane to define a resection guide in the custom arthroplasty resection guide.