Four different types of derotation braces and an elastic knee support were tested on ice-hockey players. The elastic support did not noticeably affect rotation and abduction-adduction of the knee. All four braces reduced rotation and abduction-adduction in test actions simulating sports situations. Flexion-extension was slightly affected by two of the individually made braces in one action. Running a figure eight was slower with two of the individually made braces. The best braces, one individually made and one ready-made, limited rotation and abduction-adduction effectively, but did not affect performance. Minor differences in design may account for differences in effect and may alter the protection afforded by a brace.