33 patients scheduled for bilateral total knee arthroplasty were randomized to receive a titanium alloy implant in one knee and a cobalt-chromium implant in the other knee. The purpose of this study was to examine and compare periprosthetic bone mineral density (BMD) over 2-year follow-up. When considering tibial periprosthetic BMD, scans taken in the anteroposterior (AP) plane demonstrated significantly greater BMD in the medial region in the TiN group compared to the CoCr, though both groups demonstrated a significant reduction from baseline. In addition, lateral scans demonstrated significantly greater BMD in the anterior region in the TiN group compared to the CoCR group. For the remaining tibial BMD measures, no significant differences between groups were noted in the lateral region on AP scans, or in the distal region on AP or lateral scans. When considering femoral periprosthetic BMD, no significant differences between groups were noted at any region, including anterior, central, posterior and distal regions on lateral scans. Reduction from baseline within the first were was significant within both groups in the anterior, central, and distal regions on lateral scans.