273 patients age 60 or older who had undergone unilateral total knee replacement were included in this study to determine if differing doses fo vitamin D had an effect on falls, functional outcome, and radiographic progression of osteoarthritis in the contralateral knee. Patients were randomized to receive 800IU vitamin D per day or 2000IU vitamin D per day. Outcomes of interest included falls, function (WOMAC), and radiographic progression of osteoarthritis. These outcomes were assessed at 6, 12, 18, and 24 months. The results of this study suggest that 2000IU of vitamin D3 daily offers no significant differences in the rate of falls, functional outcome, or radiographic progression of the contralateral knee when compared to a standard dose of 800IU daily.