[An experimental study on early changes of articular cartilages in subluxated patella of rabbits]

The pathogenesis and clinical progress of chondromalacia patellae have not been well studied in experimental models. We, therefore, studied the patellar subluxation produced experimentally in rabbit knees. In this model, sequential changes of the patellar cartilage were followed by simple X-rays, CT, macroscopic, histologic and scanning electron microscopic examinations up to 32 weeks. Pathological changes extending from horizontal fissures in the middle to the deep layers of the patellar cartilage and thinning of the subchondral bone were found at about six weeks after operation. The early changes of chondromalacia patellae were mostly what is called the basal degeneration, which was presumably attributed to the shearing stress on the articular cartilage. The sequential changes were not very remarkable; none of the rabbits developed OA changes by thirty-two weeks after operation. From these findings, we have that the cartilaginous changes in chondromalacia patellae progress very slowly which probably result from the vigorous repair by the cartilage and also from the acquisition of adaptability on the patellofemoral joint.