The influence of gender on knee kinematics, kinetics and muscle activation patterns during side-step cutting.

BACKGROUND It has been suggested that gender differences in the performance of athletic maneuvers is a contributory factor with respect to the disproportionate incidence of non-contact anterior cruciate ligament injury in female athletes. The purpose of this study was to evaluate gender differences in knee joint kinematics, kinetics and muscle activation during a side-step cutting. METHODS Three-dimensional kinematics, ground reaction forces (2400 Hz) and electromyographic activity (surface electrodes) were recorded during the early deceleration phase of side-step cutting in 30 healthy collegiate soccer players (15 male, 15 female). Gender differences in knee joint kinematics, peak moments, net joint moment impulse and average muscle EMG intensity were evaluated with one-tailed t-tests. FINDINGS No differences in kinematics were found. However, when compared to males, females demonstrated a smaller peak knee flexor moment (1.4 (0.8) vs. 2.1 (0.8) Nm/kg, P = 0.05) and a greater knee adductor moment (0.43 (0.5) vs. 0.01 (0.3) Nm/kg, P < 0.01) during early deceleration. In addition, females displayed greater average quadriceps EMG intensity than males (191% vs. 151% maximum voluntary isometric contraction, P = 0.02). INTERPRETATION In general, females experienced increased frontal plane moments and decreased sagittal plane moments during early deceleration. These differences are suggestive of an "at risk" pattern in that frontal plane support of the knee is afforded primarily by passive structures (including the anterior cruciate ligament). Furthermore, increased quadriceps activity and smaller net flexor moments may suggest less sagittal plane protection (i.e., increased tendency towards anterior tibial translation).