The England international suffered the problem in a collision with Javier Mascherano during his side’s 2-0 defeat to Barcelona in the Champions League on Tuesday.
Oxlade-Chamberlain underwent a scan on Thursday and Wenger says the results showed that the injury is a ‘serious’ one.
But the Gunners boss expects the 22-year-old to return to action before the end of March, allaying fears he could miss out on Euro 2016.
“We lost Chamberlain on Tuesday,” said Wenger. “His injury is quite serious and keeps him out for a few weeks. He’s seeing a knee specialist.”