Osteoclast in joint fluid


In this smear from a dog with degenerative joint disease, ther is a multinucleated cell with pink granulation compatible with an osteoclast (arrow). This suggests erosion of or damage to cartilage, exposing subchondral bone. The remaining cells are mononuclear, being a mixture of macrophages (not activated) and lymphocytes (arrowhead), with the former dominating.