Page 170 - Biomedical Engineering and Design Handbook Volume 1, Fundamentals

BIOMECHANICS OF HUMAN MOVEMENT 147

Knee Extension Moment
60
Extension
50
40
30
N-m 20
10
0
–10
–20
0 20 40 60 80 100
% Stance
FIGURE 6.18 Knee extension moment during the stance phase of natural
cadence walking. The net extension moment reveals that the quadriceps muscles are
the dominant group during stance. The initial small flexion moment is caused by the
vertical ground reaction force when the foot hits the ground.

spring, resisting the force of impact. Hence, in Fig. 6.18 we see that a substantial knee extension
moment is generated by the quadriceps muscle group to control knee flexion during this time.
Reporting the results of an inverse dynamics analysis in graphical form as we have done here
demonstrates the interdependence of the kinematic and kinetic variables. The figures are helpful
when communicating with an athlete or trainer in breaking down a movement pattern to determine
how performance might be improved. Inverse dynamics is also a valuable tool that is used to plan
surgical treatment and assess the outcome. For example, consider the case in Fig. 6.19. The right

FIGURE 6.19 Examples of a normally aligned (right
panel) and a genu varum (left panel) knee. A larger abduction
moment and reduced joint contact area for the genu varum
knee will lead to higher than normal stresses during stance.