Bruised knee.
it's pretty oobvious he hasn't fully healed from the acl surgery. It hasn't even been a full year yet and sometimes it takes longer than a year, depending on the player and how well it physically heals and how well the player deals with it emotionally.
If i were UsU I would redshirt him and allow more healing time for next year. Unlike last year, he can still take a medical redshirt since he was re injured in the first couple games.