A 4-year-old cat arrived at Kasetsart University's veterinary teaching hospital in Bangkok with its mouth stuck wide open after a suspected high-rise fall. The cat could not bring its jaws together, its lower jaw was visibly shifted, and it was blind in its right eye.
Computed tomography explained the gaping mouth. The two halves of the lower jaw had separated at the chin, the left jaw joint was dislocated, and a thin plate of bone from the left side of the jaw had slipped outside the cheekbone, wedging the mouth open. Veterinarians described the case this year in Veterinary Record Case Reports, noting that this kind of open-mouth jaw locking is uncommon in cats.
The Jaw Hooked Itself Open
Open-mouth jaw locking happens when the coronoid process, a thin blade of bone rising from the back of the lower jaw, moves to the outside of the zygomatic arch, the bony bar that forms the cheekbone. Once it catches there, the jaw cannot swing shut. A 2018 review in the Journal of Feline Medicine and Surgery describes how imaging, especially CT, helps confirm this mechanism.
In the Bangkok cat, CT showed separation of the mandibular symphysis, the joint where the two halves of the lower jaw meet at the chin, along with displacement of the left coronoid process relative to the cheekbone. The report identifies a dislocated left temporomandibular joint as the cause of the locking. Scans also found multiple fractures, including one in the right palatine bone, part of the roof of the mouth, which was in contact with tissue around the eye.
Because of the eye and neurological findings, veterinarians also performed an MRI of the brain, which showed no abnormalities in the brain tissue itself. They manually repositioned the jaw and fixed the two halves of the lower jaw together with circummandibular cerclage wires.
The combination fits what specialists have described before. In a June report in the Journal of Veterinary Dentistry, veterinarians at the University of Zaragoza in Spain wrote that the condition is often associated with looseness of the jaw joint and the chin joint, which allows the coronoid process to catch on the cheekbone. Their patient, a 5-year-old Persian cat with recurring episodes, needed surgery to trim part of the coronoid process.
Many Suspected Dislocations Turn Out to Be Something Else
The Bangkok cat did have a dislocated jaw joint, but new referral data suggest that is often not the answer when a cat cannot close its mouth. In a study published this year in the American Journal of Veterinary Research, researchers reviewed 42 cats referred between April 2020 and February 2025 for a suspected temporomandibular joint luxation.
Only six, or 14%, actually had an isolated jaw joint dislocation. The most common final diagnosis, in 19 cats, was end-stage periodontal disease. Five had malocclusion, four had a separated chin joint, and three had open-mouth jaw locking from other suspected causes. Two had jaw fractures, two had no significant findings, and one had a fused jaw joint. The authors noted that signs such as an inability to close the mouth and a shifted jaw are nonspecific.
That matters because the treatments differ. When a true dislocation is caught early, the outlook is good. A review of 21 cats treated at the University of Pennsylvania between 2000 and 2018 found that reduction succeeded in 94.7% of cases, and success was significantly linked to how quickly treatment began. Fights with dogs caused 38% of those injuries, while falls and car strikes each caused 19%. Permanent malocclusion, the most common complication, affected 24%.
Falls Injure Cats' Faces More Often Than Owners Might Expect
Cats have a reputation for landing on their feet, but falls still commonly injure their faces. A 2025 study of 1,125 high-rise syndrome cases treated at Freie Universität Berlin's small animal clinic between 2004 and 2013, which its authors called the largest such sample to date, found orofacial injuries in 51.1% of cats. Chest trauma appeared in 58.3% and limb fractures in 47.2%. Overall, 87% of the cats survived.
In an analysis of the same Berlin cases, 77% of the falls happened between April and September, when windows and balconies are more likely to be open. Secure window screens and check balconies for gaps a cat can slip through are simple ways to lower the risk.
Signs That Call for a Prompt Vet Visit
A cat that suddenly cannot close its mouth, drools, paws at its face, has a crooked jaw or refuses food needs veterinary attention, especially after a fall or a fight. Because several conditions look alike from the outside, the Penn authors noted that only diagnostic imaging provides a definitive diagnosis of a jaw joint dislocation.
The Bangkok case is a single report, and it cannot show how often falls produce this particular injury. Taken together with the new referral data, though, it underscores that an open-mouthed cat is not a one-diagnosis problem and that accurate imaging can change which treatment the animal receives.
Key Questions Answered
What happened to the cat?
A 4-year-old cat that likely fell from a height arrived with its mouth locked open. CT showed its lower jaw had split at the chin, its left jaw joint was dislocated, and part of the jaw had caught outside the cheekbone.
What is open-mouth jaw locking?
It is a condition in which the coronoid process of the lower jaw slips outside the cheekbone and gets stuck, preventing the mouth from closing. It is uncommon in cats.
How did veterinarians treat it?
They manually repositioned the jaw and wired the two halves of the lower jaw back together with circummandibular cerclage wires.
Does every cat that cannot close its mouth have a dislocated jaw?
No. In a study of 42 cats referred for a suspected jaw joint dislocation, only six had one. Severe periodontal disease was the most common real diagnosis.
How common are face injuries after falls?
In a study of 1,125 cats with high-rise syndrome, about half had orofacial injuries, and 87% of the cats survived overall.
How can owners reduce the risk of falls?
Use secure window screens and make sure balconies and terraces have no gaps a cat can slip through, especially in warmer months.
Published by Medicaldaily.com
