The Iceland international came off during last Saturday's goalless draw with Doncaster after picking up a hip injury and he missed the 1-0 defeat to Cardiff on Wednesday night.
However, he is expected to be fit to return as the Royals look for a win against struggling Posh.
Reading made it 13 home games without a victory against Cardiff - a run stretching back to January - but they did triumph at Barnsley on their last away day.
Club captain Ivar Ingimarsson was back on the bench against Cardiff after eight months out with a knee injury but Darren O'Dea is expected to remain alongside Alex Pearce in the back four.
Jobi McAnuff (back) and Chris Armstrong (knee) remain sidelined while Shane Long could be back after a knock.