The Dutchman has damaged medial knee ligaments and will be out for four to six weeks however there were fears the injury might have been to cruciate ligaments. That would have seen him sidelined for the vast majority of this season.
"His injury is a medial knee ligament," said Wenger at Monday's press conference. "At one stage we were scared it was a cruciate but we had good news and the scan was positive. But it is still a long injury."