Derry picked up an injury against Millwall last Sunday and was sent for a scan on Thursday evening where they found a 'floating bone' inside his knee.
He was operated on immediately and Kevin Blackwell is confident that the injury will not keep him out for too long.
"We found a floating object in the knee and he's had the op and hopefully it will only keep him out for between 10 to 14 days," said Blackwell on the official Leeds United website.
"It's a blow for Shaun but we have got a few good lads who can come in and it's only at times like this that you appreciate the squad you've been building."