Dietary supplements are increasingly being used for the symptomatic relief of osteoarthritis (OA). As supplements are not regulated as drugs, there is a lack of scientific support for their perceived benefits, and recent studies into their effects on articular cartilage have been conflicting. The use of supplements is becoming more widespread, thus it is in public interest to elucidate their mechanisms and effects. Subsequently this study investigates the effectiveness of two commonly used joint supplements (chondroitin sulphate; Ch and glucosamine sulphate; Gl) in chondro-protection post-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), Ch (0.3mg/ml) or Gl supplemented (0.1mg/ml) DMEM and subsequently subjected to a single impact. 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. Supernatants were analysed for IL-1β and MCP1 by ELISA at 0, 2, 4, 24 and 48h post mechanical impact. Explants in isotonic DMEM exhibited a decrease in cell viability from 79±0.05% to 56.88±3.45% at 48h post impact (p<0.01). Conversely, when treated with Ch there was no decrease in chondrocyte viability from 99.08±3.65% to 98.71±4.51% at 48h. Additionally, samples treated with Gl exhibited a minor decrease in viability from 96.66±3.69% to 82.84±4.51% at 48h, which was a significantly smaller decrease than the control samples (p<0.01). Ch and Gl treated samples both displayed a decrease in cell volume (p<0.01), from 760±61μm3 to 451±19μm3 and 523±27μm3 respectively, 2h post mechanical trauma when compared to control conditions. Additionally pre-incubation with Ch and Gl resulted in a decrease (p<0.05) in relative F-actin (61.93±3.24AU and 35.06±1.30AU respectively) when compared to non-treated samples (77.32±4.72AU) pre-mechanical trauma. Post trauma, samples treated with Ch exhibited a further decrease in relative F-actin followed by a recovery to pre trauma levels (2h post trauma: 39.44±2.84AU; 48h: 65.39±4.82AU). Conversely Gl treated samples exhibited no significant change post trauma (p>0.05) and control samples displayed a decrease with no recovery within the 48h post trauma (48h: 48.46±3.76AU). Pro-inflammatory cytokine production was significantly (p<0.05) decreased post trauma in samples treated with Ch (IL-1β: Isotonic 121.59±5.90pg/ml/g Ch 106.81±6.82pg/ml/g; MCP-1: Isotonic 1281.57±6.45pg/ml/g Ch 695.75±18.07pg/ml/g; all at 48h post trauma). These data suggest that despite inducing actin depolymerisation, Ch and Gl exhibit chondro-protective effects by reducing cell volume and decreasing the release of pro-inflammatory cytokines.