Although there have been many studies on regeneration of the articular cartilage, mechanism of regeneration has not been clarified. Some studies showed that maturity was one of the factors of successful articular cartilage regeneration.

In this study, articular cartilages in immature and mature rats were injured by the intra-articular H₂O₂ injection, and the differnece of the regeneration processes of articular cartilages in both groups was compared. For this study, 4 week-old 28 Sprague-Dawley rats(immature group), weighing 100g on an average and one year-old 28 Sprague-Dawley rats(mature group), weighing 350g on an average were used. For all rats, 0.05ml of 2% H₂O₂ was injected into the left knees four times with one week interval. In each experimental group, 4 rats were sacrificed at 1, 2, 3, 4, 6 and 7 weeks after first intra-articular injection, and tibial sides of the joints were taken for the histopathological and histochemical studies of articular cartilage.

The results were as follows:

1) In both groups, the severity of articular cartilage damage depended upon the numbers of injection.

2) Articular cartilage damage was less severe in the immature group than the mature group at 1, 2 and 3 weeks but at 4 weeks, severe destruction of articular cartilage was noted in both groups and there was no difference between two groups.

3) After 4 weeks, there were cartilage regeneration of fibrous nature and focal hyaline cartilage in immature group, but only fibrocartilaginous regeneration were observed in the mature group and there was repair process of the proteoglycans only in the immature group.

Through this study, it is concluded that the immature rats have the regeneration potentiality of damaged hyaline cartilage, while the mature rats do not have it.