Oxidative damage to lipids within the inflamed human joint provides evidence of radical-mediated hypoxic-reperfusion injury. Previous work has established the existence of a pathophysiological environment within the inflamed human joint, capable of sustaining a hypoxic-reperfusion event. Using four different assay systems (two standard and two novel) applied to synovial fluid for the assessment of lipid peroxidation, a series of studies demonstrate that exercise of the inflamed human knee promotes radical-mediated lipid peroxidation within the joint. The implication for novel antioxidant therapeutic approaches to inflammatory joint disease is discussed. 