Well X-ray don't show damage to ligaments and tendons.
Obviously the doctors would have manipulated his knee and can sometimes tell if there is any ligament damage but the only way to know for sure is MRI.
Id rather just pound an RB instead of designed QB runs for 3 yards and exposing Allen to potential injury.
Plus Allen picks up way more rushing yards when he improvises and just runs when its an obvious play call designed for him to throw