The Gunners have confirmed the severity of the issue and and the Scotsman will be sidelined for at least a month, or at the worst, six weeks, which means Arsenal's final few games could come too soon for him.
Mikel Arteta's men play their last Premier League game of the campaign against Brighton on May 23, three days before the Europa League final is due to take place. Ahead of Arsenal’s quarter-final tie against Slavia Prague, the Spaniard said: "We have to make sure first that he doesn’t need any surgery which it doesn’t look like it and if that’s the case the timeframe will be around what you said [four to six weeks].
"It could have been worse because the action looks quite scary but he is feeling better and the damage is not that bad so at the end of the day it is not the bad news that we could have waited for after the game.
"I don’t know [about playing again this season]. We’re going to have to go day by day, see how Kieran is feeling, see how that knee is reacting and how he can get close to play in time and train with the team and depending on where we are and how he is feeling we’ll make that decision."
Tierney’s diagnosis could also spell a nervy few weeks for Scotland as the 23-year-old is one of their most important players ahead of this summer’s European Championship.
On Tierney’s chances of returning in time for the Euros, Arteta said: "Again it will depend how things evolve in the next few weeks. He is so keen to play for us before the end of the season and obviously he is extremely keen to represent his country in the Euros."