Temporomandibular Joint Disorders in Dogs

The temporomandibular joint is the jaw joint, the hinged point in the jaw that is formed by two bones, named the temporal and mandible bones. The temporomandibular joint is also frequently referred to as simply TMJ.

There are two temporomandibular joints, one on each side of the face, each one working in concert with the other. TMJ plays a pivotal role in the normal chewing process, and is in fact essential for proper chewing, so that and any disease of this joint compromises the ability to make normal mouth movements and chew food. An affected animal will feel pain when closing or opening the mouth, or both. Diseases and disorders of the TMJ are referred to as temporomandibular joint disorders.

Though these disorders can occur in any dog breed, certain breeds like basset hounds are more predisposed to TMJ disorders. Open-mouth mandibular locking has been reported in Irish setters and basset hounds.

Symptoms and Types

• Difficulty opening/closing the mouth
• Mandible bone may be out of place and visible form the side of the face (deviation of the mandible bone)
• Pain when chewing food
• Vocalizing, whining while trying to eat
• Loss of appetite

Causes

• Injury or trauma causing fractures to the joint
• Stress in joint after carrying heavy objects by mouth

Diagnosis

Most of these animals are presented to their veterinarian’s with the complaint that they are unable to eat normally. You will need to begin by giving a thorough history of your dog’s health, including a background history of symptoms, when the problems first appeared, and whether there have been any previous traumas or injuries involving the mouth or head.

After taking a detailed history, your veterinarian will conduct a complete physical examination on your dog, examining the mouth, bones and the joints in the mouth. Laboratory tests will include a complete blood count (CBC), biochemistry profile, and urinalysis. The results of these tests are often found to be normal, especially if no other concurrent disease is present.

X-rays remain a valuable tool in the diagnosis of TMJ disorders, and your doctor will be likely to use this type of imaging to get a better view of the bones and joints in the face. Magnetic resonance imaging (MRI) can be used as well, and can give a better, more detailed view that standard X-ray. If your veterinarian has an MRI machine in the clinic, this may be the recommended image technique. If something more severe is suspected, such as infection or tumor, your veterinarian may also take a small sample from the muscle tissue of the jaw so that other diseases that can cause similar symptoms can either be confirmed or ruled out.