Fine structure of artificial splits in femoral condylar cartilage of the rat: a scanning electron microscopic study.

Artificial splits made in rat femoral condylar articular cartilage have been studied by SEM. Three types of split have been described; non-layered, unidirectional layered and multidirectional layered. The frequency of each type of split varies in the different regions of the condyle. Deformation and crack propagation are features of layered splits and the latter are often accompanied by exposure of fibres. The fibre pattern over the articulating surface of the rat femoral condyle, revealed by trypsin or NaOH treatment, has been determined and a correlation found between this pattern and the orientation of splits previously observed by ILM. The influence of fibre arrangement on split production is discussed and consideration given to other factors, such as mechanical stress, chondrocyte distribution or PG concentration gradients, which may determine both characteristic patterns. Further evidence is presented of the value of the pin prick method as a technique for exploring the nature of normal and abnormal articular cartilage.