The Ghana international had an operation to repair a ruptured anterior cruciate ligament and meniscus following a right knee injury.
According to a Chelsea statement, "the surgery was successful and Michael's full recovery could take up to six months".
Chelsea manager Andre Villas-Boas added: "Everyone at Chelsea wishes Michael well for his recovery. His team-mates and all the staff and I look forward to helping him return to playing as soon as possible."
Essien's setback is the third serious knee injury of his career and represents a blow to the Blues as they look to regain the English title from Manchester United after finishing a distant second, by nine points, to the champions last season.
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