Synovial osteochondroma involving the elbow of a cat

A 12-year-old spayed domestic crossbred cat presented because she would not walk down stairs. A firm swelling on the medial aspect of the elbow was detected during physical examination. The lesion was not hot or painful on palpation and the lameness was mild, but the elbow had a reduced range of motion compared with the contralateral limb.

Plain radiographs, physical findings, the appearance of the lesion at surgery and histopathological examination of biopsy specimens suggested the mass was a synovial osteochondroma arising from synovial membrane near the medial portion of the elbow joint. Resection of the lesion improved the cat's mobility and overall clinical status. At the time of writing, the cat continued to do well 18 months following surgery and was receiving standard doses of meloxicam for the concurrent elbow osteoarthritis.

Practitioners should be alert to the possibility of this benign entity. Misdiagnosis as a chondrosarcoma, for example, might conceivably lead to radical and unnecessary amputation.