The Croatia international could also miss the European Championship after he was stretchered off in the win against Quevilly at the weekend
The 22-year-old left the Coupe de France final against Quevilly on a stretcher after only 18 minutes of play. Garde said after the 1-0 victory that the setback was not serious but the centre-back still needed a CT scan to determine the full extent of his leg injury.
And after undergoing tests on Sunday Garde has now admitted that Lovren will miss the remainder of the Ligue 1 campaign.
"His season is probably over," Garde revealed to reporters.
"This is a rare injury in which the recovery time is somewhat vague at this stage."
It is not yet known how long Lovren will be sidelined for, although more details should be released in the coming days.