A method for generating a smooth mating surface model defining a mating surface of a customized arthroplasty jig, the method comprising: segmenting sagittal slices of a volumetric image of a patient bone with segmentation splines; generating an anatomically accurate model of the patient bone from the segmentation splines using at least one processor, the anatomically accurate model including anatomically accurate segmentation splines; transforming the anatomically accurate segmentation splines into mating surface contours; modifying any inadequate segments of the mating surface contours to obtain modified mating surface contours; generating an initial mating surface model of the patient bone using the at least one processor based on the mating surface contours and the modified mating surface contours; and smoothing three-dimensional cross-sections of the initial mating surface model by removing one or more peaks and valleys in at least one curve of the three-dimensional cross-sections of the initial mating surface model by removing one or more peaks and valleys in at least one curve of the three-dimensional cross-sections without encroaching into a region inside the patient bone to generate the smooth mating surface model wherein smoothing the three-dimensional cross-sections of the initial mating surface model by removing one or more peaks and valleys in at least one curve of the three-dimensional cross-sections without encroaching into a region inside the patient bone comprises: identifying a group of points extending along one of the mating surface contours, the group of points being part of points defining the mating surface contour and including a middle point disposed along the mating surface contour between a first point and a second point; identifying an extreme outward point of the points defining the mating surface contour; defining an outer boundary extending through the extreme outward point; identifying the middle point of the group of points; determining whether the middle point is inward towards the surface of the bone relative to the outward boundary; translating the middle point along a path generally perpendicular to the outward boundary to reside on the outward boundary where the middle point is inward relative to the outward boundary; and leaving the middle point in place where the middle point is on the outward boundary. segmenting sagittal slices of a volumetric image of a patient bone with segmentation splines; generating an anatomically accurate model of the patient bone from the segmentation splines using at least one processor, the anatomically accurate model including anatomically accurate segmentation splines; transforming the anatomically accurate segmentation splines into mating surface contours; modifying any inadequate segments of the mating surface contours to obtain modified mating surface contours; generating an initial mating surface model of the patient bone using the at least one processor based on the mating surface contours and the modified mating surface contours; and smoothing three-dimensional cross-sections of the initial mating surface model by removing one or more peaks and valleys in at least one curve of the three-dimensional cross-sections of the initial mating surface model by removing one or more peaks and valleys in at least one curve of the three-dimensional cross-sections without encroaching into a region inside the patient bone to generate the smooth mating surface model wherein smoothing the three-dimensional cross-sections of the initial mating surface model by removing one or more peaks and valleys in at least one curve of the three-dimensional cross-sections without encroaching into a region inside the patient bone comprises: identifying a group of points extending along one of the mating surface contours, the group of points being part of points defining the mating surface contour and including a middle point disposed along the mating surface contour between a first point and a second point; identifying an extreme outward point of the points defining the mating surface contour; defining an outer boundary extending through the extreme outward point; identifying the middle point of the group of points; determining whether the middle point is inward towards the surface of the bone relative to the outward boundary; translating the middle point along a path generally perpendicular to the outward boundary to reside on the outward boundary where the middle point is inward relative to the outward boundary; and leaving the middle point in place where the middle point is on the outward boundary. identifying a group of points extending along one of the mating surface contours, the group of points being part of points defining the mating surface contour and including a middle point disposed along the mating surface contour between a first point and a second point; identifying an extreme outward point of the points defining the mating surface contour; defining an outer boundary extending through the extreme outward point; identifying the middle point of the group of points; determining whether the middle point is inward towards the surface of the bone relative to the outward boundary; translating the middle point along a path generally perpendicular to the outward boundary to reside on the outward boundary where the middle point is inward relative to the outward boundary; and leaving the middle point in place where the middle point is on the outward boundary.