In this study, participants will be randomly picked (as in the toss of a coin) to be in one of four treatment groups. Treatment in this study will last 6 months. Participants in the first group will receive a placebo during all 6 months. A placebo is a substance that looks like the study drug but is inactive. Participants in the second group will receive a placebo during Months 1-3 and Celecoxib during Months 4-6. Participants in the third group will receive Celecoxib during Months 1-3 and placebo during Months 4-6. Participants in the fourth group will receive Celecoxib during all 6 months. Neither the participant nor the participant's doctor will know to which treatment group the participant was assigned. Participants have an equal chance of being assigned to any of these groups.