The Canaries held Claude Makelele's side to a 1-1 draw as they ramped up their preparations for the forthcoming Sky Bet Championship campaign.
Anthony Pilkington got Norwich's goal but there were concerns over Howson's health when he came off late in the first half with a knee injury.
Adams told the club's official website: "He kicked through and he's just tweaked his knee. He's in there with an icebag on it, and he said it doesn't feel too bad. It's the sort of one where 24 hours is key, so we'll see in the morning.
"Jonny Howson is a key player for us, so fingers crossed he's okay."
Meanwhile, new signing Lafferty missed out entirely but Adams was keeping his fingers crossed over the striker's problem.
He added: "The scan showed no tear on the muscle, just some bleeding which is best-case scenario. He's in a protective boot purely as a precaution. Best-case scenario is three to four days for Kyle."