Controversy exists regarding the efficacy of prophylactic knee braces for football players. Starting players from eight high school football teams were studied, and the injury rate for players who wore prophylactic knee braces was compared with the injury rate of players who did not wear prophylactic braces. In the braced group, 23 knee injuries occurred in 21,640 exposures to contact during a 4-year period. In the nonbraced group, 26 knee injuries occurred in 19,484 exposures during the same time period. No statistically significant difference in injury rates or severity of injuries between the two groups occurred. Considering these results and the expense of prophylactic knee bracing, the authors recommend that sports medicine practitioners do not advocate prophylactic knee bracing for high school football players.