Djourou in action for Arsenal in August before his injury
Arsenal defender Johan Djourou could be out of action for up to six months after he underwent knee surgery.
The 22-year-old Swiss international had the operation on his knee cartilage in Geneva on Friday, the Swiss Football Federation said.
Djourou had to leave a Swiss training camp before a friendly against Italy last month because of knee pain.
Before he underwent surgery, Arsenal manager Arsene Wenger had hoped Djourou would only be out for a month.
During an encouraging start to the season Arsenal's first-choice centre-back pairing has been William Gallas and Thomas Vermaelen, with Mikael Silvestre and Philippe Senderos providing defensive cover.
If Djourou is only out for six months it gives him a chance of playing in the 2010 World Cup if Switzerland qualify for the finals.
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