Roofe suffered the injury during last week’s 2-1 win at home to Swansea City and underwent scans on Monday morning to confirm the extent of the damage.
The Whites have not put a timescale on the forward’s likely return but the club insist the 26-year-old still has a chance of featuring in the Championship run-in.
Leeds said: “Leeds United forward Kemar Roofe will face a period on the sidelines following confirmation that he damaged knee ligaments during the win over Swansea City at Elland Road. Roofe will work hard with the medical team at Thorp Arch to return to action as quickly as possible.”
Roofe completed the duration of last Wednesday’s clash against Swansea but complained of pain in his knee the following morning and was sent for scans after examinations suggested he had damaged ligaments.
The forward has netted 14 goals this season but Roofe has been playing as a no 10 following the recent return of striker Patrick Bamford from a knee injury of his own.
United’s season has been ravaged by injuries with Roofe facing his second spell out having missed six matches in September and October with a calf strain. Leeds sit third in the table and have 14 games remaining, starting with Saturday’s clash at home to Bolton Wanderers.
Pablo Hernandez, Tyler Roberts and Izzy Brown - himself recently back from injury - are other options for Leeds in the No 10 role.