['Forty-three patients who had undergone cementless THA were randomly assigned to receive no osteoactive drug or oral risedronate for 6 months. Postoperative decrease of BMD in the risedronate group was significantly lower than that seen in the control group in zones 1, 2, 3, 6, and 7.', 'Proximal bone resorption around the femoral stem often has been observed after total hip arthroplasty (THA), could lead to late stem loosening. We previously reported the efficacy of etidronate on periprosthetic bone resorption after cementless THA. Recently risedronate is suggested to be effective for the prevention and treatment of for osteoporosis. The purpose of the present study was to evaluate the effects of risedronate on periprosthetic bone loss after cementless THA.', 'Forty-three patients who had undergone cementless THA were randomly assigned to receive no osteoactive drug (21 patients) or oral risedronate 2.5 mg/day (22 patients) for 6 months. Three patients were eliminated from the risedronate group because of dyspepsia. Periprosthetic bone mineral density (BMD) in seven regions of interest based on the zones of Gruen et al. was measured with dual energy X-ray absorptiometry at 3 weeks and 6 months postoperatively.', 'At 6 months after surgery, postoperative decrease of BMD in the risedronate group was significantly lower than that seen in the control group in zones 1, 2, 3, 6, and 7 (p < 0.05, p < 0.01, p < 0.01, p < 0.05, and p < 0.05, respectively).'] Does risedronate reduce postoperative bone resorption after cementless total hip arthroplasty?