A method of planning an arthroplasty procedure on a femur and tibia of a patient. The method includes receiving a first two-dimensional image of the femur and the tibia, and identifying, in the first two-dimensional image, a proximal femur feature, a distal tibia feature, and a bone contour. The method further includes running a transformation process to align a bone model representative of the femur and the tibia into a coordinate system with the first two-dimensional image, the bone model having a bone model contour that is aligned with the bone contour of the femur and the tibia in the first two-dimensional image. And the method further includes applying an implant model to the bone model in order to determine coordinate locations for the arthroplasty resection.