Mechanical trauma through repetitive, high-impact sport contributes to the onset of osteoarthritis. Hypertonicity protects chondrocytes from mechanical trauma1 suggesting a role for cell volume in this process. Since the 5-lipoxygenase inhibitor REV5901 inhibits chondrocyte volume regulation, this study was designed to investigate whether this compound exerts a chondro-protective effect following mechanical trauma. Cartilage explants were dissected from the joints of 18-21 month old steers (obtained with ethical permission) into DMEM. Explants were incubated for 1h in either: isotonic (280mOsm), hypertonic (380 mOsm), DMSO supplemented (5μl/ml) or 50μM REV5901 DMEM and subsequently subjected to a single impact as previously described (Bush et al., 2005). Chondrocyte viability, volume and relative F-actin concentration were determined by confocal microscopy and data expressed as mean ± s.e.m; (Student T-test: p<0.05), n=45 cells each from 5 distinct experiments. Supernatant from the explants was analysed for inflammatory cytokines by ELISA at 0h, 2h, 4h, 24h and 48h post mechanical impact. Explants in isotonic or DMSO supplemented DMEM exhibited a decrease in cell viability from 79±0.05% & 83±1.63% to 45±2.52% & 50±3.45% at 48h post impact; p<0.05 and p<0.05 respectively. Conversely, when incubated with hypertonic DMEM or 50μM REV5901 there was no decrease in chondrocyte viability from 89±3.65% to 90±4.51% to 93±2.63% to 86±3.34% at 48h. REV5901 incubated samples displayed a decrease in cell volume (p<0.01) from 1547±61μm3 to 1011±19μm3 2h post mechanical trauma when compared to control conditions. Additionally pre-incubation with REV5901 resulted in an increase (p<0.05) in relative F-actin (208.70±4.85AU) when compared to non-treated samples (185.00±6.36AU) prior to mechanical trauma and a significantly less acute decrease post trauma (REV5901 171.00±5.76AU; Isotonic 64.69±3.16AU both at 48h post trauma). Cytokine changes relative to control were significantly (p<0.05) decreased post trauma in samples pre-incubated with REV5901 (IL-1β: Isotonic 1.30±0.18pg/ml/g REV5901 0.55±0.21pg/ml/g; IL-10: Isotonic 1.18±0.09pg/ml/g REV5901 0.90±0.11pg/ml/g; MCP-1: Isotonic 1.46±0.20pg/ml/g REV5901 0.60±0.07pg/ml/g; all at 2h post trauma). These data suggest that REV5901 exhibits a chondro-protective effect in an in vitro model of mechanical trauma by reducing cell volume and decreasing the release of inflammatory cytokines.