Concentration of cytokines in the serum. Although the concentration of cytokines in the synovial fluid after the 100-μl lavage was below detection limit for all cytokines in all samples, the concentrations of cytokines in sera were detectable. Significant differences among groups were not identified, although a general trend for higher concentrations of IL-1α, IL-1β, and GM-CSF in medial meniscus transection (MMT) rats may exist (nonsignificant). Moreover, serum concentration of IL-6 tended to be higher in rats with MMT surgery (open diamond) than that in naïve controls (solid diamond; P = 0.072), but not medial collateral ligament (MCL) sham animals (shaded diamond). Raw data are presented. ^Differences between surgical groups that are near-significant at a level of 0.1 <P ≤ 0.05.