Since the clinical benefit of knee braces has yet to be defined, discussion about braces after reconstructive surgery of the anterior cruciate ligament remains controversial. The use of prophylactic braces in sport did not prove to be effective. In ACL insufficient knee joints, the operative treatment is preferred over the use of functional knee braces. Therefore, the postoperative rehabilitation presents the main application of braces. Modern operative techniques with an initial strong fixation of the ACL graft make a functional postoperative treatment without external fixation possible. In the presented meta-analysis of the literature about knee braces, results from clinical and experimental studies are compared. No published clinical data have shown that braces have any effect on postoperative outcome after ACL-reconstruction. Also, no evidence of a significant bracing effect could be demonstrated in the experimental in vivo or in vitro studies, except a limited stabilizing function for lower shear stress below the physiological loads. Consequently, the systematic use of braces in the rehabilitation after ACL reconstruction cannot be recommended.