26 patients who underwent total knee arthroplasty (TKA) were randomized to one of two groups: alendronate and calcium supplementation for 1 year postoperatively, or calcium alone for 1 year postoperatively. The purpose of this study was to examine the effect of alendronate on periprosthetic bone mineral density (BMD) postoperatively. Follow-up was performed for 7 years. The alendronate group demonstrated significantly higher distal femoral metaphyseal BMD at 6 months and 1 year than calcium control, though decreased thereafter and was not significantly different from calcium alone at 7 years. Alendronate had a significantly positive effect on proximal lateral tibial metaphyseal BMD throughout follow-up.