What causes “Open locks”?The lower jaw, mandible, is connected to the socket – (known as glenoid fossa) at the TM joints just in front of the ear holes. The TMJ capsule is the ligamentous connection between the head and the mandible. Its function is to keep the mandible connected to the skull and limit the maximum opening of the jaw. This ligament has to be over stretched through partial tearing of the fibers for the condyle (ball) to get out of the fossa (socket).
Many people have a condition of condyle coming out of the fossa momentarily called ‘subluxation’. This may cause a popping sound at full opening of the mouth but usually causes no pain. So people usually ignore this. It is only when the condyle comes out of the socket and stays out of the socket, then it is considered “dislocated”. This is called “open lock” since the jaw stays stuck in an open position.
This is quite painful due to the stretched ligaments, especially the longer the jaw stays dislocated from the socket and stays stuck in the open position. The muscles near the jaw joint also go into painful spasm. (see Zach's case history and Natalie's case history).