In the example you give the following happens:
The victim takes his MC (and the result of that MC is applied).
The victim suffers the attack as described in the Knob hit action.
The victim suffers the blow effect and may have to take another maneuver check.
If the victim fails the second MC (and was already knocked down) he "rolls" over the ground and is repositioned.
Keep in mind that if the victim fails his first MC and is knocked down he counts as being knocked down by the second MC (the one coming from the attack) and the Crowd Mood (and victim's and attacker's Pop) will be modified accordingly.