The Norway-based player was absent in the Black Stars opening game against Ivory Coast because of a knee setback.
But he returned to full training on the day Michael Essien suffered a knee injury during their preparation for the must-win tie against Burkina Faso.
Annan started training with his Ghana teammates on Saturday but switched into full gear on Sunday, boosting his chances of playing at the Africa Cup of Nations.
The Norway-based player has been sidelined by a hamstring injury he sustained before the tournament started.
Annan trained with the team on Saturday evening in Luanda and was fit for another session the next day.
The 23-year-old has been battling with injuries in the Black Stars camp as a knee problem pegged him back during the team’s pre-tournament training.
Six key Ghana players are out of the tournament because of injuries.