In sports involving pivoting and landing, female athletes suffer knee injury at a greater rate than male athletes. Proprioceptive deficits in control of the body's core may affect dynamic stability of the knee. Female, but not male, athletes who suffered a knee injury during a 3-year follow-up period would demonstrate decreased core proprioception at baseline testing as compared with uninjured athletes. Cohort study (prognosis); Level of evidence, 2. Study subjects were 277 collegiate athletes (140 female, 137 male) who were prospectively tested for core proprioception by active and passive proprioceptive repositioning. Athletes were monitored for injury for 3 years. An ANOVA and multivariate logistic regression were used to test whether core proprioception was related to knee injuries in athletes. Twenty-five athletes sustained knee injuries (11 women, 14 men). Deficits in active proprioceptive repositioning were observed in women with knee injuries (2.2 degrees ) and ligament/meniscal injuries (2.4 degrees ) compared with uninjured women (1.5 degrees , P or= .05). Uninjured women demonstrated significantly less average error in active proprioceptive repositioning than uninjured men (1.5 degrees vs 1.7 degrees , P