Christine E. Whitten, Anyone Can Intubate, 2nd Ed, Medical Arts Publications, 1990

CAN THE PATIENT OPEN HIS OR HER MOUTH WIDE ENOUGH FOR 3 FINGERS?

Limited Mobility of the Mandible: Opening the mouth requires two movements: opening the hinge joint on a vertical axis and then sliding the angle of the jaw forward. Check both since arthritis, scar tissue, and spasm of the masseter muscle can impair either movement.