The 26-year-old was due to take part in yesterday's match at Burnley but pulled out in the morning.
Speaking after their 2-1 loss to the league-leading Clarets at Turf Moor, Adkins told the club's official website: "Garath is going to get his knee assessed on Monday. He's been carrying an injury for the last couple of weeks.
"I didn't name my team for today until this morning and Garath was in my plans, but unfortunately his knee was sore yesterday and, having traveled up last night, a seven hour journey has probably not helped him on that front.
"This morning it was still sore and he wasn't fit enough to go and play today - so that will be assessed and we'll see where we go from there."
Defeat left Reading just outside the Championship playoff places in seventh.