Introduction & Objective: The most frequent site of injury in football is the knee. In this study the value of prophylactic knee braces in reduction of MCL injuries was evaluated.

Materials & Methods: In this prospective cohort study we evaluated 11480 athlete-exposure that lasted 30 minutes. After the explanation of study method to coaches and athlete we gave them two kind of study questionnaires. After data collection we analyzed data with SPSS 10. Results: In this study 149 injuries happened out of which. 28 were knee injuries (21 in unbraced athletes and 7 in braced athletes (P=0.21) and 23 were knee ligamentous injuries (16 in unbraced athletes and 7 in braced athletes (P=0.662). There were 16 MCL injuries (11 in unbraced athletes and 5 in braced athletes). The relative risk in this study was 0.454. We evaluated the severity of ligamnetous injury and there was no significant difference between the two groups (P=0.5).

Conclusion: In conclusion in this study we found that the prophylactic knee braces had no positive effect in prevention of knee injuries. Some epidemiological studies with large samples and longer period should be designed to discover the real effect of these braces in knee injuries prevention.