During terminal stance and pre-swing, the external knee moment is what?

During terminal stance and pre-swing, the external knee moment is what?

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

Answer: (B)

The main concept here is how ground reaction forces create an external moment at a joint. In terminal stance and pre-swing, the body's weight shifts and the ground reaction force line moves in relation to the knee such that it tends to bend the knee. This produces an external knee flexion moment. The muscles then must generate an internal extension moment to control the knee as you push off and prepare to swing the leg. Dorsiflexion and abduction describe movements at other joints or planes (ankle motion and frontal-plane loading), not the direction of the knee’s sagittal-plane moment, so they aren’t describing the knee torque in this phase. An external extension moment would occur if the force acted in front of the knee, which isn’t the typical pattern during these parts of the gait cycle.

The main concept here is how ground reaction forces create an external moment at a joint. In terminal stance and pre-swing, the body's weight shifts and the ground reaction force line moves in relation to the knee such that it tends to bend the knee. This produces an external knee flexion moment. The muscles then must generate an internal extension moment to control the knee as you push off and prepare to swing the leg.

Dorsiflexion and abduction describe movements at other joints or planes (ankle motion and frontal-plane loading), not the direction of the knee’s sagittal-plane moment, so they aren’t describing the knee torque in this phase. An external extension moment would occur if the force acted in front of the knee, which isn’t the typical pattern during these parts of the gait cycle.