It is possible to dislocate the jaw on only one side, a condition medically known as a unilateral mandibular luxation. This occurs when the lower jaw bone, or mandible, moves out of its normal position within the temporomandibular joint (TMJ) on just one side of the face. The dislocation involves the mandibular condyle—the rounded end of the jawbone—slipping out of the glenoid fossa, the socket in the temporal bone. This displacement is a distinct injury from a fracture or a bilateral dislocation, which affects both sides simultaneously.
How the Jaw Joint Allows for One-Sided Dislocation
The architecture of the jaw joint permits a unilateral dislocation because the two temporomandibular joints function independently, though connected by the mandible. Each TMJ acts as a hinge and a gliding joint, allowing for the complex movements needed for chewing, speaking, and yawning. The joint surfaces are separated by a dense fibrocartilaginous articular disc, which aids in the smooth gliding motion of the condyle within the socket.
When a dislocation occurs, the mandibular condyle most commonly slides forward, or anteriorly, past a bony ridge called the articular eminence. This anterior luxation often happens when the mouth is opened excessively wide, such as during a large yawn or a dental procedure. Since the left and right joints are not rigidly fused, trauma or forceful movement can affect only one side, leaving the opposite side correctly seated.
The powerful surrounding muscles, including the masseter and temporalis, then go into spasm, trapping the condyle out of position in front of the articular eminence. This muscle spasm prevents the jaw from easily returning to its proper place.
Recognizing the Signs of a Unilateral Jaw Dislocation
The most visually apparent sign of a unilateral jaw dislocation is distinct facial asymmetry or distortion. This misalignment occurs because muscles on the dislocated side pull the lower jaw into a fixed, open position while the unaffected side remains stable.
The chin shifts sharply toward the side that is not dislocated, creating a noticeably crooked appearance. The person experiences an inability to close the mouth completely, leaving it in an “open lock” position. Patients often report intense, localized pain near the ear or the preauricular area on the affected side.
A palpable indentation or hollow may be felt just in front of the ear on the side of the dislocation. Difficulty with basic functions like speaking or swallowing is common due to the fixed, open mouth position and improper bite alignment.
Immediate Care and Medical Reduction
If a unilateral jaw dislocation is suspected, seek professional medical help immediately. Gently support the lower jaw with a hand or soft bandage to minimize movement, and apply a cold compress to the joint area to reduce swelling and pain. Patients must avoid any attempt to manipulate or force the jaw back into place on their own, as self-reduction can cause serious damage to the joint capsule, ligaments, and nerves.
A medical professional, such as an emergency room physician or an oral surgeon, must perform a procedure known as manual reduction. This closed reduction technique often involves administering muscle relaxants or local anesthetics to overcome the strong muscle spasms holding the jaw out of position.
The physician uses specific downward and backward pressure on the mandibular molars to guide the condyle past the articular eminence and back into the glenoid fossa. Following a successful reduction, the patient is advised to follow a soft diet and avoid wide mouth-opening for several weeks to allow the joint structures to heal. Follow-up care is necessary to prevent recurrence, often including exercises and instruction on proper jaw support during activities like yawning.