A 12 year old greyhound recently presented to the Cambridge clinic in distress, after falling at home & crying in pain. The dog was incredibly agitated & panting. It was noticed that the patella (knee cap) had an unusual amount of movement & there was crepitus (crunching) when the stifle and hock were flexed. The thigh was swollen, so x-rays were taken and diagnosed a pathological fracture of the femur due to weakening of the bone from an osteosarcoma.

Osteosarcomas are an aggressive form of bone cancer that primarily affect large or giant breed dogs, such as greyhounds, rottweilers, and Saint Bernards. Osteosarcomas may be found in any bones, but typically develop in the long bones, such as the limbs (usually “away from the elbow and towards the knee”). Signs of osteosarcoma include pain, swelling, or limping in the affected limb. The condition is most common in middle-aged to older dogs, though it can occur in younger dogs as well.

The exact cause of osteosarcomas in dogs remains unclear, but genetic predisposition, rapid bone growth, and trauma are considered potential contributing factors. The cancer typically spreads (metastasises) to other parts of the body, particularly the lungs, making early detection crucial for improving prognosis.

Diagnosis can involve a combination of physical examination, x-ray, and biopsy to confirm the presence of cancerous cells.

On x-ray, a bone with an osteosarcoma will appear “moth-eaten”. This is due to a process called osteolysis, which is resorption of bone matrix, and is essentially the reverse process of bone growth and development.

This leaves the affected area of the bone weakened and therefore vulnerable to a “pathological fracture”. Treatment of osteosarcomas is usually limited to amputation of the affected limb, however development of new tumors in other areas of the skeletal system is unfortunately very common.