From Valve Developer Community
This entity is obsolete; its use is discouraged and it may only exist/function in older engine branches.
ai_goal_injured_followis a point entity available in Half-Life 2: Episode One. This entity appears to have been part of an idea where Alyx would follow the player while she was injured. Alyx would occasionally flinch, have special "injured" animations for most tasks, and tell the player to slow down if they get too far ahead of her. The entity does not function at all, currently.