A 10-year-old Doberman pinscher was presented with a 4-month history of pro
gressive recurrent lameness of the hindleg. Physical examination revealed a
slightly painful swelling in the distal aspect of the left patella. Radiog
raphs showed areas of bone lysis in the apex of the patella and dense miner
alization in the patellar ligament. After examination of a biopsy the histo
pathological diagnosis was osteosarcoma.