Methods for treating or preventing diseases classified as any of grade 1 to 3 according to the ICRS classification of osteoarthritis, classified as grade 1 to 3 according to the Kellgren-Lawrence classification of osteoarthritis, or classified as grade 1 to 3 according to the Outerbridge classification of osteoarthritis, include administering to a subject in need thereof a therapeutically effective amount of treatment agents or preventive agents containing an anti-Fas IgM antibody as an active ingredient to alleviate osteoarthritis symptoms by inhibiting the production of cartilage matrix degrading enzymes and by increasing the production of cartilage matrix.
