Per the Official Site:
The tendonitis in his knee flared up last week. It is not considered serious.
"He has had some soreness in his knee, but he said he could run and work out on it," Gibbs said. "He's on his weight [training] program. We'll see how the running goes. We'll see how quickly we can get him back.
"The main thing now is to get it taken care of now. What we don't want is this when we go to camp."
Portis has been continuing to rehab from offseason shoulder surgery. The shoulder is holding up well through the rehab, team officials said.