FGF18 is known to stimulate the proliferation of chondrocytes, bone, and nervous tissue, resulting in repair of diseased tissue. When an IL-1 antagonist is administered in addition to FGF18, the effects on the IL-1 mediated disease and also, the effect on cartilage, bone, and nervous cell proliferation, are found to be greater than administration of FGF18 or the IL-1 antagonist alone. The present invention encompasses a pharmaceutical composition that combines FGF18 with IL-1 antagonist and methods of treating IL-1 mediated disease using this pharmaceutical composition.