Jawbone Enlargement in Dogs

Maxilla and Mandible are the upper and lower parts of a dog's jaw. These two parts are joined at the two ends by the temporomandibular joint (TMJ). TMJ is responsible for up and down movements of the jaw. Dogs use their cheek muscles to move the TMJ in order to open and close their mouths.

Craniomandibular Osteopathy or jawbone enlargement refers to a condition where excess bone formation occurs along the mandible and TMJ. This non-cancerous growth causes severe pain specially during eating and prevents the dog from opening or closing its mouth properly. 

This condition occurs in developing puppies of three to eight months. Certain breeds including Scottish Terriers, Cairn Terriers, and West Highland White Terriers. Other breeds that have higher incidence rate are Labrador Retrievers, Great Danes, Boston Terriers, Doberman Pinschers, Irish Setters, English Bulldogs, and Boxers.

The age of onset of clinical signs is usually three to eight months.  The most common signs of craniomandibular osteopathy (CMO) include swelling of the lower jaw, which is painful to the touch, drooling or excessive salivation and difficulty grasping things using the mouth. Affected dogs may also experience pain and limited movement when opening their mouth. As a result they tend to eat less and consequently lose weight, another sign of craniomandibular osteopathy. Where the disease causes enlargement in the long bones (e.g. in the legs), lameness and/or painful swelling of the limbs may become obvious. During periods where the bones are actively growing, affected animals may also show signs of fever.

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