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Why is my senior dog suddenly in pain when opening his mouth?

Updated On September 23rd, 2025

Pet's info: Dog | Jack Russell Terrier | Male | neutered | 10 years and 4 months old | 25 lbs

Hello, our 10yr old male Jack Russel Terrier suddenly is experiencing pain when trying to open his mouth. He seems fine otherwise, no swelling or mouth odor. He just cries out when he tries to open.

1 Answer

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on June 22nd, 2018

There is a condition in older dogs called masticatory myositis. It is an auto immune disease where, for some reason, the immune system attacks the muscles of the cheek. In the early stages, it hurts when the muscles of the cheeks move, and it is pain that stops the mouth from opening. Over time, ongoing damage causes scar tissue to from that stops the muscle from stretching. It could be that Brody has this condition, and it is treatable with high doses of steroids. I can't say for certain this is what is causing him pain when he opens his mouth, but you could speak to your vet to see if this could be a cause.

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