Robinson could miss the rest of the season after a scan showed torn cartilage.
The 20-year-old did not play in Saturday's defeat by Inverness and will miss the match against St Mirren on Wednesday night - a dress rehearsal for the Scottish Communities League Cup final on March 17.
Hearts manager John McGlynn said: "Scott Robinson has picked up a recurrence of a knee injury and has a tear in his meniscus, which is not great.
"It was an injury that recurred during the Hibs game (on January 3).
"We tried to give it some time but it came back again. He had a scan yesterday which showed up exactly what it was.
"Worst-case scenario, he would need a wee tidy-up (operation).
"It may well be you can nurse it through to the end of the season but we are talking ifs and buts.
"He has another opinion to get from a specialist and we'll talk with Scott and see what's the best way to go about it."