Effect of three prophylactic knee braces on knee flexion angle and external knee adduction moment in three types of single -leg landing tasks

Effect of the knee brace stiffness on lower limb mechanics, which may protect anterior cruciate ligament, under different landing tasks remains still unknown. The purpose of this study was to determine the effect of three prophylactic knee braces on the knee flexion angle and external adduction moment under three types of single-leg landing conditions.

Fifteen men performed single-leg landing under three different landing foot orientation tasks (30° toe-out, 30° toe-in and neutral conditions) for three different types of brace stiffness (rigid, semi rigid and simple one). A non- braced condition was included as a baseline measure. kinematic data were captured using a six video-camera motion capture system synchronized with a force platform.

No significant interaction effects of brace stiffness and the landing tasks on flexion angle (P = 0.059) and external knee adduction moment (P = 0.103) were observed. Stiffer braces (rigid and simi rigid) could increase knee flexion angle by 20% as compared to non-braced condition. Furthermore, external knee moment was significantly increased during landing with foot 30° toe-out orientation as compared to the neutral condition (P <0.001).

finding showed that effect of the braces on the variables is independent of landing foot orientations. Stiffer braces could increase knee flexion during landing while toe-out landing may increase external knee moment leading to higher risk of ACL injury.