Aaron Ramsey is set to spend six weeks on the sidelines[GETTY]
The Wales international picked up the knock during the 1-1 draw with Tottenham on Saturday, and had to be helped as he limped off the field.
The news will come as a major blow for Arsene Wenger, who could also be without Jack Wilshere and Mikel Arteta, who are suffering from ankle and calf injuries respectively.
Team of the week - Gameweek 6
Ramsey is a concern. He's usually a resistant boy
Arsene Wenger
The Frenchman will be without the trio for Wednesday night's Champions League clash with Galatasaray, with Wenger saying: "I don't know how long they will be out but they will be out next week.
"I think Ramsey is a hamstring, and Arteta is a calf. Wilshere is an ankle.
"Ramsey is a concern. He had a good rest this week, I didn't play him against on Southampton on Tuesday night, it's a surprise because he's usually a resistant boy."
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