The sensation of the jaw “locking” when opening or closing the mouth is a startling and uncomfortable experience, often associated with the temporomandibular joint (TMJ). This temporary inability to move the jaw freely is a common issue. Understanding its mechanics and reasons can help in seeking relief and treatment.
How the Jaw Locks
The temporomandibular joint, or TMJ, functions like a sliding hinge, enabling the diverse movements of the jaw, such as chewing, speaking, and yawning. Each person has two TMJs, situated on either side of the head, directly in front of the ears. Within each joint, a small, oval-shaped articular disc made of fibrocartilage acts as a cushion between the jawbone (mandibular condyle) and the skull (temporal bone). This disc is crucial for the smooth gliding and rotational motions of the jaw.
Jaw locking results from a disruption in the normal movement of this articular disc or the jawbone. The disc can become displaced, most commonly moving forward (anteriorly) from its proper position relative to the condyle. When the mouth opens, if this displaced disc does not return to its normal alignment, it can obstruct the joint’s movement, leading to a “closed lock” where the mouth cannot open fully. Conversely, an “open lock” occurs when the jawbone slides too far forward out of its socket, preventing it from returning to its original position and making it impossible to close the mouth.
Underlying Reasons for Jaw Locking
Jaw locking frequently results from temporomandibular joint disorders (TMDs), conditions affecting the jaw muscles, TMJs, and associated nerves. Disc displacement, where the articular disc shifts from its normal position, is a common reason. If the disc displaces but then returns to its correct place during jaw movement, it’s known as disc displacement with reduction, often accompanied by clicking or popping sounds. When the disc displaces and does not return, it results in disc displacement without reduction, which can cause a true jaw lock and limited mouth opening.
Muscle spasms are another frequent cause of jaw locking, often leading to a condition called trismus, where the jaw muscles tighten severely, restricting mouth opening. These spasms can stem from various factors, including stress, teeth grinding (bruxism), or clenching. Jaw trauma or injury, such as a direct blow or dislocation, can also lead to locking by damaging the joint structures or causing bleeding within the joint. Excessive joint looseness, known as hypermobility, can contribute to open jaw locks, particularly when the mouth opens very wide, as the jaw condyle may slide out of its socket.
Certain medical conditions can also play a role. Arthritis, including osteoarthritis or rheumatoid arthritis, can affect the TMJ, leading to changes in the joint’s bone shape and potential locking. While rare, systemic bacterial infections like tetanus can cause severe, widespread muscle spasms, including those in the jaw, leading to prolonged and painful jaw locking. Often, the exact cause of TMDs, including jaw locking, remains unclear, suggesting a complex interplay of genetic, psychological, and physiological factors.
Immediate Steps and Relief
When the jaw locks, remaining calm is important; anxiety can intensify muscle tension. Applying a warm compress to the sides of the face for 10-20 minutes can relax jaw muscles. Follow this with gentle jaw movements, such as slow side-to-side or back-and-forth motions, without forcing the jaw. Gently massaging the affected jaw muscles may also provide relief.
Adopting a soft food diet, like yogurt, soup, and mashed potatoes, can reduce jaw strain, allowing the joint and surrounding muscles to rest. Over-the-counter pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, can help manage pain and inflammation.
If the jaw remains locked for more than a few minutes, or if pain is severe and persistent, seek professional medical attention. Persistent pain, difficulty eating, or frequent locking indicate a need to consult a dentist or doctor.
Professional Diagnosis and Treatment Options
A healthcare professional, such as a dentist specializing in temporomandibular disorders or an oral surgeon, can diagnose jaw locking. Diagnosis typically involves a physical examination of the jaw, assessing movement and listening for sounds like clicking or popping. Imaging techniques, such as X-rays or MRI, may visualize joint structures, including the articular disc, and identify issues like displacement or degeneration.
Treatment approaches vary depending on the underlying cause and severity of the condition. Custom oral appliances, such as splints or mouthguards, are often prescribed to stabilize the jaw, reduce teeth grinding or clenching, and help reposition the disc. Physical therapy can be beneficial, involving exercises to improve jaw flexibility and strength, manual therapy to release muscle tension, and posture adjustments. Medications may include stronger prescription pain relievers, muscle relaxants to alleviate spasms, or tricyclic antidepressants in low doses for chronic pain management. Injections, such as corticosteroids for inflammation or botulinum toxin type A (Botox) to relax jaw muscles, can also provide relief.
Surgical interventions, including arthrocentesis (flushing the joint) or arthroscopy (minimally invasive joint repair), are considered when conservative treatments are ineffective. In rare, severe cases, open-joint surgery or total joint replacement might be necessary.