Quadriceps/Hamstring Co-activation during walking following Anterior Cruciate Ligament Reconstruction

Undergraduate: Zain Syed

Faculty Advisor: Troy Blackburn
Department: Exercise & Sport Science

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Anterior cruciate ligament injury and surgical reconstruction (ACLR) incur a high risk of knee osteoarthritis (OA). While simultaneous activity of the quadriceps and hamstring muscles is required for normal walking gait, excessive co-activation may lead to altered biomechanics that contribute to OA development. Therefore, the purpose of this study was to evaluate relationships between quadriceps/hamstrings co-activation and gait biomechanics linked to knee OA development in individuals with ACLR. Walking gait biomechanics and electromyography of the quadriceps and hamstrings muscles were assessed in 26 individuals with ACLR. Quadriceps/hamstrings co-activation index, peak vertical ground reaction force (vGRF) magnitude and loading rate, and knee joint kinematics and moments were calculated during the preparatory and load acceptance phases of gait. The co-activation index was not correlated with vGRF characteristics. However, greater preparatory co-activation was associated with greater knee varus moment (r= 0.398, p = 0.046) and greater load acceptance co-activation was associated with greater knee varus moment (r = 0.392, p = 0.049) and peak knee varus angle (r = 0.404, p = 0.043). The varus motion and moment apply compressive force to the cartilage in the medial knee compartment where knee OA is more prevalent. As such, the results of this investigation suggest that greater quadriceps/hamstrings co-activation may play contribute to the mechanical pathogenesis of PTOA.