Granero is on-loan at Real from QPR.
Real Sociedad released an official statement on their club website confirming the news of the injury.
"The MRI scan done this morning discovered a ruptured anterior cruciate ligament and medial meniscus injury in Granero's right knee," read the statement.
"This injury will require surgical repair. The player will perform a physical therapy focused on stimulating and maintaining the neuromuscular control of the joint."
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