How do you know if you have a orbital fracture below the eye?

Thats serious: The only way to know is by xray or ct scan of skull/face. However, a clue is having an injury to the eye or nearby face, followed by double vision or seeing the eyes not tracking together. Unlike sturdy bones of rest of face, orbital bones are almost paper thin. Under extreme force can "blow out", then the fracture captures the lower eye muscle causing one eye to get "stuck" in certain positions.

Ct scan: Symptoms will possibly be Diplopia after blunt trauma and maybe numbness of the cheek and gum on the same side as the trauma. A ct scan will tell you definitively. Coronal views give the best info for evaluating the orbital floor