A Multicenter, Double-blind, Randomized, Active-controlled, Parallel Group, Noninferiority Study Comparing 75mg Risedronate Dosed on 2 Consecutive Days Monthly With 5mg Daily Risedronate in the Treatment of Postmenopausal Osteoporosis as Assessed Over 24 Months.

To confirm the non-inferiority of 75 mg risedronate tablets taken on 2 consecutive days per month as compared to 5 mg risedronate tablets taken daily in increasing bone mass in lumbar spine in postmenopausal women with osteoporosis. To confirm the efficacy of 75 mg risedronate tablets taken on 2 consecutive days per month in postmenopausal women with osteoporosis in increasing bone mass in proximal femur, femoral neck and femoral trochanter and decreasing bone resorption. To confirm general safety of 75 mg risedronate tablets taken on 2 consecutive days per month as compared to 5 mg risedronate taken daily.