Yawning can cause a jaw dislocation, though this is uncommon for most people. The involuntary opening of the mouth during a yawn can push the jaw past its normal limit. This usually concerns individuals with underlying anatomical or muscular vulnerabilities. When dislocation occurs, the lower jawbone slips out of its correct position at the temporomandibular joint (TMJ), the hinge connecting the jaw to the skull.
The Anatomy of Jaw Movement
The temporomandibular joint (TMJ) is formed by the articulation between the lower jawbone, or mandible, and the temporal bone of the skull. The rounded end of the mandible, called the condyle, rests in a socket known as the glenoid fossa. A small, flexible articular disc sits between the condyle and the fossa, allowing for smooth movement when chewing, speaking, or yawning.
During the process of opening the mouth, the condyle first rotates and then glides forward and downward, sliding across a bony ridge called the articular eminence. A normal, wide yawn pushes the condyle to the very edge of this eminence. A true dislocation, or luxation, occurs when the condyle moves completely past the articular eminence and becomes locked in the front of the joint.
A partial displacement, known as subluxation, occurs when the condyle slips out but spontaneously snaps back into place. In a full dislocation, the jaw muscles, particularly the lateral pterygoid, can spasm and prevent the condyle from returning to the fossa, resulting in an “open lock.” This anterior dislocation is the most common type and is caused by extreme mouth opening, such as during a wide yawn.
Factors That Increase Dislocation Risk
Yawning becomes a risk factor when combined with pre-existing conditions that affect joint stability. Individuals with joint hypermobility, often called “double-jointed,” have naturally elastic ligaments. This ligamentous laxity means the joint capsule supporting the TMJ may be too loose to keep the condyle securely in place during maximal opening.
Certain systemic connective tissue disorders, such as Ehlers-Danlos Syndrome, involve generalized weakness that increases the risk of recurrent TMJ dislocations. A history of temporomandibular disorders (TMD) or previous dislocations also predisposes an individual to future episodes. Once the joint has dislocated, the ligaments and capsule are stretched, making the joint less stable.
Chronic jaw clenching or teeth grinding (bruxism) can lead to muscle incoordination and fatigue in the masticatory muscles, further destabilizing the joint. The structure of the TMJ itself can also be a factor. Some people have a naturally shallow mandibular fossa or a less prominent articular eminence, which provides less physical barrier to prevent the condyle from gliding too far forward during actions like yawning or laughing.
Recognizing the Signs of Jaw Dislocation
A dislocated jaw presents with distinct physical signs that differentiate it from simple jaw soreness or muscle strain. The most obvious symptom is the inability to close the mouth; the jaw will be fixed in an open position, often called an “open lock.” This inability can also cause drooling because the muscles necessary for swallowing cannot function properly.
The jaw may appear visibly shifted or crooked, deviating to one side in a unilateral dislocation. Pain is severe and localized just in front of the ear, where the TMJ is situated. Individuals may also notice that their teeth do not align correctly, resulting in an abnormal bite.
Difficulty with speaking is another common sign, as the fixed position of the jaw prevents the necessary movements for clear articulation. If the dislocation is accompanied by a loud popping or crunching noise near the ear, it suggests the condyle has slipped out of its normal position. These signs require prompt attention to safely reduce the joint.
Immediate Actions and Prevention
If a jaw dislocation occurs, the immediate action is to seek professional medical or dental help. A dislocated jaw is considered a medical emergency because leaving it untreated can lead to prolonged muscle spasms and increased swelling, making reduction more difficult. Attempting to force the jaw back into place without proper training is not recommended and can cause further damage.
While waiting for medical assistance, a cold pack can be applied to the area to help manage swelling and pain. Once a healthcare provider reduces the jaw—a procedure involving gently manipulating the mandible back into its socket—the individual will be advised to restrict jaw movement. This includes eating only soft foods for several days and being cautious to avoid wide mouth openings.
For individuals with a history of recurrent dislocations, prevention focuses on controlling the extent of mouth opening. A simple technique is to place a fist gently under the chin whenever a wide yawn or laugh is anticipated, which physically limits the range of motion. Consulting a specialist, such as an oral surgeon or a physical therapist, can lead to long-term management strategies, including custom-made occlusal splints or exercises to strengthen the jaw muscles.