This invention relates to methods of treatment of osteoarthritis, and especially to treatment of this condition with cyclic peptidic and peptidomimetic compounds which have the ability to modulate the activity of G protein-coupled receptors. The compounds preferably act as antagonists of the C5a receptor, and are active against C5a receptors on polymorphonuclear leukocytes and macrophages. Particularly preferred compounds for use in the invention are disclosed.