Abstract
Summary This study reports on the early findings in experimental hemarthrosis. Biochemical and histological analyses show the first signs of cartilage degeneration secondary to the presence of blood in the joint, and this for a certain duration. The lower limits of amount and duration, necessary to produce a reaction in synovium and cartilage are determined. Evidence is also given that the production of degradative enzymes, by the synovium especially, plays an important role, in the early phase of cartilage degeneration. A few hypotheses are discussed.