[Initial degeneration of the articular cartilage in the rat]

The authors have investigated the process of degeneration of articular cartilage in its early stages using an experimental model which has made it possible to show, for the first time, the effects of a mechanical parameter other than excessive pressure--that is excessive friction. The two healthy hips in twenty anaesthetised young rats were used for the study. One hip was kept immobile and served as a control. The other was subjected to physiological movements of flexion and extension continuously and without rest for periods varying from twelve hours to seven days. The articular cartilage of the two femoral heads was examined by light microscopy, transmission electron microscopy and scanning electron microscopy. A new fact was demonstrated. Cartilage wear is also associated with the simple movement of two joint surfaces over one another without any muscle contraction being involved. In the genesis of cartilage wear, excessive friction alone seems to be as important as excessive pressure.