But head coach Gregor Townsend admitted he faces a lengthy spell on the sidelines, which will see him miss a number of games, including the 1872 Cup clashes against Edinburgh.
"We're disappointed for Rob that he's going to miss a number of games, especially as he has been in great form this season," said Townsend.
Harley has started seven of Glasgow's eight GUINNESS PRO12 games this season, scoring a try in the home win over high-flying Connacht back in September.
And having missed out on selection for the World Cup, he will now also be absent from Vern Cotter's Scotland squad during the Six Nations because of the injury.
Glasgow travel to Edinburgh on Sunday for the first of the two Scottish derbies at BT Murrayfield, before welcoming their rivals to Scotstoun the following week.
Currently sixth in the table despite playing a game fewer than every team bar Leinster, Glasgow could move into the play-off places with wins over Edinburgh.
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