Kirkpatrick tweeted about the injury on Tuesday night, apologizing for the circumstances.
NFL Network has learned from a source close to Kirkpatrick that the first-round draft pick fractured a bone in his knee. He is expected to miss six weeks and likely the start of the regular season.
Kirkpatrick injured the knee while preparing for training camp, creating a situation where the Bengals could potentially withhold pay from the former Alabama standout. He will fail the team's physical and land on the physically unable to perform list.