The Northern Ireland international was stretchered off before half-time in the weekend's shock defeat by Annan after a challenge from Steven Swinglehurst.
He has had the problem area scanned and the results were not positive. Now Shiels is heading south to get an expert opinion on the damage.
Manager Ally McCoist said: "It's not great. He was in a lot of pain on Saturday night and he was heavily iced up but he was in pain again the next morning when I spoke to him.
"He went for a scan and the results are not great so he is heading down to London tomorrow to see a specialist.
"We will learn the next step after that but it's not looking too good.
"When I look back at the incident with him, if Dean had hit the ball first time it would have been better. But hindsight is a wonderful thing.
"I am loathe to make any comment on the situation until we hear from the specialist."
On the bright side, McCoist is optimistic that David Templeton will be fit to return to the side at Elgin on Saturday.
He said: "Temps is still struggling a little with an Achilles problem he picked up last Thursday but I'm still hopeful that he will be available for the weekend.
"We will give him every chance and we will need to wait and see."