The effect of knee brace misalignment on the anterior cruciate ligament: An experimental study

Protective knee braces are used for rehabilitation or prevention. Due to poor patient compliance or slippage, the brace might be misaligned with the knee axis. Does a misaligned knee brace stress the anterior cruciate ligament? It is an experimental study. A strain sensor was implanted on the anterior cruciate ligament in eight limbs. The limbs were mounted in a knee simulator, muscle forces were applied and a cyclic motion from 10° to 60° flexion was performed under three conditions: unbraced, braced and with a misaligned brace. The outcome measures were anterior cruciate ligament strain and three-dimensional kinematics of the knee joint. The correctly aligned brace significantly reduced the anterior cruciate ligament strain at 10° compared to the unbraced condition from 0% to ？1.54% (standard deviation？=？1.4). The misaligned brace neutralised the effect of bracing to ？0.06% (standard deviation？=？1.1) anterior cruciate ligament strain. At 60° flexion angle, bracing had no statistically significant effect on the anterior cruciate ligament strain compared to the unbraced knee: ？2.58% (standard deviation？=？0.8) versus ？1.64% (standard deviation？=？1.0). The anterior cruciate ligament in the misaligned braced knee at 60° flexion with a strain of ？1.1% (standard deviation？=？0.9) was significantly more stressed than in the correctly aligned condition. An effect of bracing on knee kinematics was not detected. A correctly aligned knee brace reduced anterior cruciate ligament strain. By contrast, a misaligned brace tended to increase the anterior cruciate ligament strain compared to the unbraced knee. The correct alignment of the brace was identified as a key factor decisively influencing the effectiveness of bracing