Medard went off in the second half of Les Bleus' 23-17 victory over Scotland at the weekend and a subsequent scan revealed he had suffered damaged cruciate and anterior ligaments.
The 25-year-old Toulouse player said on his official Twitter account:
"The operation is booked for Monday and my unavailability will be from six to nine months."
Medard scored a try in France's victory at Murrayfield and his absence for the remainder of the Six Nations and beyond is a significant blow to coach Philippe Saint-Andre's hopes of leading his troops to the Grand Slam.
Saint-Andre has turned to Medard's Toulouse team-mate Clement Poitrenaud to deputise at full-back for this weekend's rearranged clash with Ireland in Paris.
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