Defender has not featured for club or country since the European Championship and manager Paul Lambert admits concern over lack of progress
Dunne picked up the injury representing Ireland at the European Championship and the 33-year-old is not expected to play in the Premier League before the turn of the year.
Villa manager Paul Lambert revealed on Friday: "The injury is just not clearing up and this has got to be a real nightmare for Richard.
"As a footballer you want to be informed what is the problem. But we cannot seem to get to the bottom of is causing the trouble at the moment.
"He will now go to see someone else and hopefully we will finally be able to get to the bottom of the problem."