LONDON: Chelsea midfielder Michael Essien will be out of action for up to six months after undergoing knee surgery, the Premier League club said on Monday.

The Ghanaian suffered a cruciate ligament injury last week during pre-season training.

“Everyone at Chelsea wishes Michael well for his recovery,” Chelsea manager Andre Villas-Boas told the club's website.

“His team mates and all the staff and I look forward to helping him return to playing as soon as possible.”

Essien, 28, was sidelined for more than six months in 2008 with a similar injury.