It is exaggerated to illustrate the point of too much hyperextension.
It would be hard to take a step forward with this much hyperextension of the knee joint.
An example of too much hyperextension for illustration
purposes only.
Proper hyperextension is just enough to keep the knee
from buckling forward.
If this were a mechanical knee, it would be adjusted
too far
behind the center of body weight (see red indicator
line).