We investigated the effects of exogenous phosphatidylcholine (PC) and non-steroidal diclofenac supplementation on polymorphonuclear cell influx in carrageenan-induced arthritis in rats. The microcirculatory consequences were evaluated by a novel method developed for direct intravital microscopic observation of the synovial membrane. Arthritis was induced by injection of a mixture of 2% lambda-carrageenan and 4% kaolin into the knee joints and the animals were treated orally with PC (150 mg/kg twice daily), sodium diclofenac (0.5mg/kg twice daily) or saline vehicle. Intravital videomicroscopy was used to investigate the leukocyte-endothelial interactions directly in the synovial membrane at 6h after the challenge. The inflammation-induced thermal and mechanical secondary hyperalgesic reactions were assessed at 24h, and the knee volume changes at 48h after the insult. The development of arthritis was accompanied by a significant increase in the number of adherent leukocytes in the synovial postcapillary venules, but this increase was reduced significantly (by approximately 40%) by PC, and slightly (by 22%) by diclofenac treatment. The perivascular infiltration of the neutrophil leukocytes and the intercellular adhesion molecule-1 (ICAM-1) expressions were reduced only by PC treatment. The significant decrease (45%) in the thermal nociceptive latency, the 3-fold increase in the mechanical touch sensitivity and the knee cross-sectional area (which was increased by 35% by the arthritis induction) were significantly ameliorated by both treatments. The present study demonstrated the anti-inflammatory effects of PC in experimental arthritis. The therapeutic potential may be linked to the reduction of neutrophil leukocyte-mediated microcirculatory inflammatory reactions.