Objective To investigated the effects of combination treatment with ibandronate (IBN)and pulsed electromagnetic field (PEMF) on bone turnover, bone mineral density (BMD), bone microarchitecture and biomechanical properties in ovariectomized(OVX) rats.Methods Fifty 3-month-old rats were ovariectomized or sham operated, and randomly divided into five groups (Sham, OVX, IBN, PEMF and COM groups).Weekly ibandronate was administered subcutaneously or/and daily PEMF were performed to the respective groups from the day after surgery.After 12-week treatments, biochemical parameters, BMD,microarchitecture parameters, and biomechanical properties were examined.Results Combination treatment with IBN and PEMF significantly reduced serum TRACP5b more than either monotherapy with IBN or PEMF.On the other hand, serum BALP also significantly increased in OVX group compared to Sham group.It was not significantly changed following monotherapy with IBN or PEMF, or combination treatment with IBN and PEMF compared to OVX group.Monotherapy with IBN or PEMF, and combination treatment with IBN and PEMF significantly increased BMD of L5 vertebral body(p < 0.01, p < 0.05, p< 0.01, respectively) and the right femur(p < 0.01, p < 0.05, p < 0.01, respectively) compared to OVX group.Additional, BMD of L5 vertebral body in COM group was significantly higher than that in IBN or PEMF group(p < 0.05, p < 0.05, respectively).However, the effects of combination treatment with IBN and PEMF to increase BMD of the femur were not significantly different from those of each monotherapy.With respect to L4 vertebral bodies,BV/TV, Tb.N, and Tb.Th were significantly lower, and Tb.Sp were significantly greater in OVX group compared to Sham group (p<0.01, p<0.01, p<0.01, p<0.01, respectively).Monotherapy with IBN or PEMF, and combination treatment with IBN and PEMF significantly increased BV/TV (p < 0.01, p < 0.05, p < 0.01, respectively), Tb.N (p < 0.01, p <0.01, p < 0.01, respectively), and Tb.Th (p < 0.01, p < 0.05, p < 0.01, respectively), and significantly reduced Tb.Sp (p < 0.01, p < 0.05, p < 0.01, respectively) compared to OVX group.Further, combination treatment with IBN and PEMF showed higher values on BV/TV (p < 0.05, p < 0.01, respectively) and Tb.N (p < 0.05, p < 0.01, respectively) in L4 vertebral body than monotherapy with IBN or PEMF.With respect to the proximal tibia, BV/TV, Tb.N, and Tb.Th significantly decreased, and Tb.Sp significantly increased in OVX group compared to Sham group (p<0.01, p<0.01, p<0.01, p<0.01, respectively).Similarly, monotherapy with IBN or PEMF, and combination treatment IBN and PEMF significantly increased BV/TV,Tb.N, and Tb.Th, and significantly reduced Tb.Sp in OVX rats.However, the effects of combination treatment with IBN and PEMF to increase BV/TV, Tb.N, and Tb.Th, and to reduce Tb.Sp were not significantly different from those of each monotherapy.Monotherapy with 1BN or PEMF, and combination treatment IBN and PEMF significantly increased maximum load (p < 0.01, p < 0.01, p < 0.01, respectively) and energy to failure (p <0.01, p < 0.01, p < 0.01, respectively) compared to OVX group.Further, combination treatment with IBN and PEMF showed higher values on maximum load (p < 0.01, p < 0.01,respectively) and energy to failure (p < 0.01, p < 0.01, respectively) in L5 vertebral body compared with monotherapy with IBN or PEMF.Similarly, 3-point bending test showed that ovariectomy significantly decreased maximum load and energy to failure of the femur.Treatment of OVX rats with either monotherapy with IBN or PEMF, and combination treatment prevented the decrease in the femur.However, the effects of combination treatment with IBN and PEMF to increase maximum 1oad and energy to failure were not significantly different from those of each monotherapy.Conelusion These results demonstrate that combination treatment with ibandronate and PEMF has a more favorable effect on the lumbar spine in ovariectomy-induced osteoporosis than either monotherapy.