One indicator of joint degeneration may be chondrocyte viability. The relationship between articular cartilage loading and chondrocyte viability has historically been determined using articular cartilage explants that are loaded in-vitro. In these tests, large amounts of cell death have been measured for peak loading values that are well within the normal physiological range. However, it seems unlikely that in an intact joint, everyday loading would cause substantial cell death. Therefore, the purpose of this study was to investigate the relationships between controlled in-vivo physiological loading, in-vivo impact loading, and cell viability.

Cell death observed following the muscle-induced loadings was the same for all three loading protocols, and was the same compared to the unloaded controls. The impact loading group showed a significant increase in cell death for both the patella and femoral groove when compared to matched controls (p<O.05). These findings indicate that maximal muscular loading of the in-vivo joint does not cause chondrocyte death, whereas non-physiological impact loading causes cell death.