Abstract: The present invention provides an arthroplasty supporting information calculation method for supporting diagnoses of a patient with knee disordered and total joint replacement to a total knee component, and an arthroplasty supporting information calculation program, and an arthroplasty supporting information calculation system. In an arthroplasty supporting terminal of the present invention, photographed X-ray images are acquired using X-ray irradiation mechanisms and a dedicated cassette base, Approximate three-dimensional data of a patient's bones is then created by transforming a display image of three-dimensional data of CT of the patient and/or sample bones to match the X-ray image in which the patient's bones are photographed. Three-dimensional coordinate values are then determined for this approximate three-dimensional data of the patient's bones. From these three-dimensional coordinate values, parameters are determined for evaluating positional relationships between at least two bones.