Disclosed is a composition for treating a joint disease, which is characterizedby comprising, as an active ingredient, a univalent metal salt of alginic acidwhich has an endotoxin level reduced to such an extent that an inflammation orattach of fever is not substantially induced. It becomes possible to providea composition for treating a joint disease, which has an effect of protectinga cartilage from a mechanical stimulus, an effect of preventing the degeneration/deformationof a cartilage caused by friction or an inflammation, an effect of repairing adamaged part in an cartilage, an effect of preventing an inflammation or a painin ajoint tissue, an effect of preventing the degeneration of a synovial tissue,and an effect of preventing the destruction of a bone or cartilage.
