If during the course of a battle your character gets knocked out and then healed, they will remain unconscious until the end of the encounter unless roused. A KO'd character is considered to be helpless.
Waking Someone from a KO
Someone in an adjacent square may spend a move action to physically rouse someone who was knocked out yet now has 0 or more hit points.
If you are still heavily injured, waking from a KO may be significantly more difficult than waking up from sleep.
Waking from a KO requires a successful Perception check. The minimum penalty to this check is -10 for being asleep. This penalty is increase 1:1 for every point by which your current HP total falls short of 10.
Awakened from a KO
Once you have been roused from a KO, you will be considered 'surprised' during the round in which you awaken unless your perception check beats the DC by 10 or more.
Newly awakened characters have their initiative count reset to the point in the round when they awoke. Such a character will typically be prone and is considered flat-footed until they have acted.