1. A method of manufacturing a custom arthroplasty resection guide, the method comprising: generating a three dimensional femur bone model from MRI knee coil two dimensional images, wherein the knee coil images include a knee region of a patient; identifying a hip center and a femur knee center in MRI body coil two dimensional images, wherein the body coil images include a hip region of the patient and the knee region of the patient; causing the three dimensional femur bone model and hip center and femur knee center to generally correspond with each other with respect to location and orientation; defining relative to the three dimensional femur bone model a femoral mechanical axis via the femur knee center and the hip center; identifying a most distal condylar point of the three dimensional femur bone model; defining a distal plane that is orthogonal to the femoral mechanical axis in a coronal view of the three dimensional femur bone model, wherein the distal plane also passes through the most distal condylar point; defining a resection plane that is parallel to the distal plane and proximally offset from the distal plane; and using data associated with the resection plane to define a resection guide in the custom arthroplasty resection guide.