نيروهاي ماهيچه يي و معضلي زانو در حين برخاستن از حالت نشسته

KNEE MUSCULAR AND JOINT FORCES WHILST RISING FROM A DEEP SQUAT

In spite of numerous studies conducted on the biomechanics of the knee joint, the muscular and joint forces in activities containing deep flexion have been rarely investigated. In this study, the knee joint forces, whilst rising from a squat position, were analyzed using a two-dimensional model of the lower extremity. The model included the ankle, tibiofemoral, patellofemoraI and hip joints, plus nine independent groups of muscles around these joints. The dynamic equilibrium equations for the foot, tibia, femur and patella, yielded a system of indeterminate equation, including 8 equations and 11 unknowns, following the omission or combination of some equations in order to reduce the unwanted unknowns. The required kinematics data were obtained by videography and the surface reaction forces were measured using a force plate. The system of indeterminate equation was solved using non-linear optimization. The sum of the third power of the muscle stresses, which minimizes muscle fatigue, was chosen to be the objective function. Results indicated that the maximum contact force in the tibiofemoral joint was 7.5 times the body weight and occurred at the deepest knee flexion angle. In the patellofemoral joint, the maximum contact force appeared at a 70 degree knee angle, with a magnitude of 4 times the body weight.