The Republic of Ireland international initially suffered the setback during Euro 2012.
Dunne has undergone two operations to try and resolve the groin injury and has finally received the green light to step up his fitness work.
But Villa boss Paul Lambert is unsure when Dunne, signed from Manchester City in a £6 million deal four years ago, will be ready for a first team recall.
He said: "Richard is back in training and it's his first time since the European Championships really.
"Will he be back soon? I'm not sure really because he's got to get up to speed with training and get some games under his belt.
"He's still a wee bit away."
Dunne has endured a nightmare time with injuries during 2012 and missed the final three months of last season with a broken shoulder.
But he insisted: "The last operation I had seems to have really worked.
"I've been lucky not to have too many injuries during my career but it's been several months where I've not been fit."