86 patients scheduled for total knee arthroplasty were randomized to surgery completed with either the use of custom cutting blocks or standard instruments. The purpose of this study was to compare femoral component rotation and tibial component rotation between the two groups. Mean deviation in femoral component rotational alignment, and the incidence of outliers in femoral rotational alignment, did not significantly differ between groups. In contrast, mean deviation in tibial component rotational alignment, and the incidence of outliers in tibial rotational alignment, were significantly lower in the CCB group.