Cardinals coach Steve Wilks told reporters on Friday that Bucannon suffered a hyperextended knee and would be undergoing an MRI exam, per the team's official website.
Bucannon, who is entering his fifth season with Arizona, was hurt while trying to avoid contact during Thursday's practice session.
After wide receiver Brice Butler made a sliding catch on a short pass from Sam Bradford, an oncoming Bucannon attempted to leap over Butler. Instead, his knee slammed into Butler's helmet.
Bucannon was able to walk off the field after he was down for a moment, and defensive coordinator Al Holcomb was not concerned that the injury is serious.
"He's fine. He's a tough player and I'm not worried about him," Holcomb told the Arizona Republic. "He's fine."
A first-round draft pick (No. 27 overall) of the Cardinals in 2014, Bucannon spent most of his first two seasons at safety before he was shifted to linebacker for the last two seasons.
Bucannon has missed seven games over the last two seasons because of ankle injuries. He appeared in 12 games in 2017, registering 82 tackles, two forced fumbles and one sack.