An Injury is a type of Condition. It is a physical ailment that the investigator may gain during the course of the game.
An injury can be removed through a Rest Action, when the investigator rolls a die and may discard on a successful roll.
Injuries trigger upon , and require the investigator to roll a check, then flip the card if the roll fails.
The four types of injuries are Head Injury, Back Injury, Internal Injury, or Leg Injury. If a Head Injury triggers, it will always be discarded after it's effect is applied. A Leg Injury will usually flip, but might be discarded. A Back Injury or Internal Injury will usually be discarded, but might flip instead.
A Head Injury will prevent the player from recovering Sanity during rest while they have it. The other three types of injuries do not impede the character unless flipped.