During midstance, the external knee moment is best described as producing which knee motion?

During midstance, the external knee moment is best described as producing which knee motion?

• A. Flexion
• B. Extension
• C. Abduction
• D. Adduction

Answer: (B)

The force acting on the leg during midstance creates a rotation about the knee that tends to straighten it. In midstance, the body’s weight is directly over the stance leg and the ground reaction force is positioned so that it would rotate the knee toward extension if not restrained. That external torque is an extension moment, and the knee position is near full extension as weight is transferred through the limb. Muscles then modulate this external torque to control how quickly and how much the knee continues to extend. A flexion moment would occur if the load’s line of action were in front of the knee, and abduction/adduction refer to movements in the frontal plane rather than the sagittal knee flexion/extension motion.

The force acting on the leg during midstance creates a rotation about the knee that tends to straighten it. In midstance, the body’s weight is directly over the stance leg and the ground reaction force is positioned so that it would rotate the knee toward extension if not restrained. That external torque is an extension moment, and the knee position is near full extension as weight is transferred through the limb. Muscles then modulate this external torque to control how quickly and how much the knee continues to extend.

A flexion moment would occur if the load’s line of action were in front of the knee, and abduction/adduction refer to movements in the frontal plane rather than the sagittal knee flexion/extension motion.