[Importance of the subchondral space for development of chondromalacia patellae--morphologic study of joint cartilage of the rabbit patella after experimental ischemia].

The aetiology of chondromalacia patellae and especially the importance of the subchondral space have not been clarified to date. However, clinical findings yielded pointers to a connection between degenerative changes of the articular cartilage and an influence exercised by the subchondral space. In our experiments we performed an operative ischaemia of the patella with interruption of the vascular inflow and outflow on 40 adult rabbits for exactly defined times (2 weeks, 6 weeks, 3 months, 6 months). The examinations were carried out using the plastination method, histology, transmission electron microscopy, and scanning electron microscopy. Marked changes can be seen from the third month onwards: disappearance of the tidemark, degeneration of the cartilaginous cells (formation of clusters) and onset of trachomatous keratitis. These degenerative changes progress further in the animals of 6 months of age. The results indicate that metaplasia of the tidemark plays a significant part in the pathogenesis of degenerative changes of the cartilage. Hence, chondromalacia patellae can be caused by subchondral vascularisation disorders.--This is, therefore, a new concept for the aetiopathogenesis of chondromalacia patellae, a disease pattern that is of great importance in sports orthopaedics.