A single impact load to a diarthrodial joint can cause permanent damage to the cartilage extracellular matrix (ECM), including surface fissures, loss of proteoglycan, cell death and a subsequent pre-disposition to osteoarthritis (Bush et al., 2005, Scott & Athanasiou, 2006). Chondrocytes being the sole resident cell-type in cartilage are responsible for the maintenance of the ECM therefore, as these cells do not divide it is vital to find a mechanism that protects chondrocytes from the effects of impact and thus prolongs their viability. Full-depth cartilage was excised from bovine metacarpal-phalangeal joints (18-24 months of age; obtained from the local abattoir) under aseptic conditions into DMEM. Explants were incubated with 5μM calcein-AM and 1μM propidium iodide for 30 min and impact experiments performed by drop-tower with a single impact of 0.131J. Samples were incubated alone or in the presence of REV5901 (50M, 30mins). Cell viability was determined at 0, 5, 10, 20 & 30mins post impact by confocal laser scanning microscopy (CLSM) and quantified using an automated method with Imaris 7.0 ‘Spots’ as previously described (Nedelcheva et al. 2008). Actin organisation was measured using Alexa-488 phalloidin labelled chondrocytes by CLSM, whilst RT-PCR evaluated alterations in cofilin and profilin mRNA levels. Amplification products were visualized by ethidium bromide fluorescence on 2% agarose gels and changes in expression quantified. All data are expressed as Mean ± s.e.m. *P<0.05 vs. control, n = 4 determination in triplicate. Impact led to a decrease in chondrocyte viability of 11.23 ± 1.24% at 30mins, this was significantly reduced in chondrocytes pre-treated with REV5901 and caused a reduction in cell death by 51% to 5.44%± 0.59% (p<0.001; Student’s t-test). REV5901 caused an increase in cortical actin staining by 20% to 78.72 ±3.99 AU within the superficial zone of articular cartilage (P<0.01; Student’s t-test) with no significant alterations observed in the mid and deep zones with values of 61.17 ± 4.25 AU and 47.50 ± 2.12 AU respectively. When comparing the differences between the mid and deep zone no significant difference was observed (P>0.05). RT-PCR of mRNA extracted from REV5901 treated chondrocytes indicated alterations in cofilin and profilin mRNA compared to untreated chondrocytes. There was no significant difference detected in gelsolin mRNA. These data highlight that REV5901 protects chondrocytes from acute trauma due in part to chondro-protective polymerisation of the actin cytoskeleton. Therapeutic modulation of the actin modulation and the pathway that REV5901 is involved in could offer novel therapeutic opportunities for prevention of irreversible cartilage damage from acute impact trauma and minimize pre-disposition to osteoarthritis.