Erosive polyarthritis of the left and right tarsal joints, and left proximal and distal interphalangeal joints consistent with feline rheumatoid arthritis. The severity of the osteolysis in the left tarsus (distal arrow) may also represent joint neoplasia. The primary differential for the increased intramedullary opacity (proximal arrow) in the left tibia should be extension of neoplastic disease from the tarsal region.
L. Armbrust, DVM, 2nd year radiology resident
Craniocaudal view of the left tarsus