A method of calculating leg length discrepancy of a patient including: receiving patient bone data associated with a lower body of the patient； identifying anatomical landmarks in the patient bone data； orienting a first proximal landmark and a second proximal landmark relative to each other and an origin in a coordinate system； aligning a first axis associated with a first femur and a second axis associated with a second femur with a longitudinal axis extending in a distal-proximal direction, wherein the first and second distal landmarks are adjusted according to the alignment of the first and second axes； calculating a distance between the first and second distal landmarks in the distal-proximal direction along the longitudinal axis； and displaying at least one of the distance or a portion of the patient bone data on a display screen.
