RR-PO-0964

Monday 16:00, Palau de Congressos, Exhibition Hall  [Display No. 769]

ELECTROMYOGRAPHIC AND KINEMATIC ANALYSIS OF A VALGUS POSITION WITH KNEE JOINT. -IMPLICATION FOR ANTERIOR CRUCIATE LIGAMENT INJURY-. Kato S, Urabe Y, Kawaguchi K, Onari K; Health Sciences Major, Graduate School of Medical Science, Hiroshima University. Hiroshima. Japan. PURPOSE: One of the anterior cruciate ligament (ACL) injury mechanisms is a valgus/varus moment about the knee or an internal/external rotation of the leg. The Biomechanical study measured the in situ force in the ACL, on human cadaveric knees. When the valgus torque was applied externally, the in situ force decreased. When the same torque was applied internally, the in situ force increased. However, both of which are comparing lower than the load of failure. Thus, we predicted that muscle activation is involved in failure. The purpose of this study was to determine whether there was a significant increase electromyographic activities in valgus position of the knee.  RELEVANCE: We assume that the mechanism of injury to the ACL involves internal forces that are generated by the leg muscles. This study provides information for the mechanism of ACL injuries.  METHODS: Twenty college student volunteers (10 women and 10 men) had no known pathologic knee conditions. Valgus torque was applied during the motion of forward-step. Electromyographic activity (surface electrodes) of the vastus lateralis, vastus medialis, rectus femoris, biceps femoris, and medial hamstring (semimembranosus/semitendinosus) muscles were recorded. Kinematics analysis with knee angle was done by The Has-200 high-speed camera and analyzed their software (Detect Co.).  ANALYSES: The mean, standard deviation of EMG (percentage maximum voluntary contraction [%MVC]) and the corresponding knee flexion angle at forward-step(valgus position/neutral). Valgus position and neutral of EMG (%MVC) were compared using a paired t-test.  RESULTS: The results of muscle activation was significantly higher in the valgus position than in the neutral position (p<0.05). Foot strike occurred at 60°of knee flexion, the vastus medialis muscle activation for valgus position was about 160%MVC, while biceps femoris muscle activity was about 70%MVC.  CONCLUSION: Muscle activation was increased in valgus position. We consider that the mechanism of injury to the ACL involves internal forces that are generated by the leg muscles.