Do Oral Contraceptives Protect Against ACL Injuries in Female Athletes

The purpose of this research study is to examine the impact of one type of commonly used birth control pill on blood levels of relaxin and measure changes in knee movement to determine whether there are changes in joint instability (indicating the knee is less stable) that may predispose female athletes to injury. Women not on hormonal birth control will also be enrolled to analyze differences between athletes on and not on birth control and to evaluate typical relaxin levels and knee laxity when birth control pills are not used.