Osteosarcoma

Osteosarcoma is bone cancer, and it is a disease of big dogs. In a UK case-control study of 1,756 cases, 27 breeds had increased odds compared with crossbreds, almost all of them larger breeds, while 30 mainly smaller breeds had reduced odds; breeds bred for long legs and large body mass were the ones at risk¹. Heavier breeds have higher cancer mortality generally².

It usually appears in a leg, most often near the wrist, shoulder, knee or hock, as a lameness that does not improve with rest and a firm, painful swelling. Because the bone is weakened, a sudden severe lameness can mean a fracture through the tumour. Any lameness in a large senior that lasts more than a week or two, or a swelling on a limb, needs an X-ray rather than a course of anti-inflammatories alone.

Treatment options range from amputation with chemotherapy to limb-sparing surgery, radiation and palliative pain control. Dogs cope with three legs better than most people expect, and pain control alone can give comfortable weeks to months¹.

This is general information, not a diagnosis. Your vet knows your dog.

Sources

1. Dog breeds and body conformations with predisposition to osteosarcoma in the UK: a case-control study (Edmunds GL et al.). Canine Medicine and Genetics 8:2, 2021 (peer reviewed). Accessed 2026-09-22.
2. Mortality in North American dogs from 1984 to 2004: an investigation into age-, size-, and breed-related causes of death (Fleming JM, Creevy KE, Promislow DEL). Journal of Veterinary Internal Medicine 25(2):187-198, 2011 (peer reviewed). Accessed 2026-09-22.