"It's exciting and it's what I wanted," said Carruthers, who is sidelined with a thigh injury.
"Obviously I know the club from before, I'm pleased to be back and I can't wait to get going again. It's like coming home."
Dons boss Karl Robinson added: "I understand some fans might be thinking 'why have we signed a player who is injured but we're building for the future?'.
"He is part of the long-term strategy here and that's shown with his three-year deal.
"He's an exceptional talent and one day I believe he will be back showcasing his ability at the top."
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