Abstract:

BACKGROUND: Knee joint trauma results in knee instability and movement track changes, which lead to the degradation of articular cartilages. The main component of articular cartilages, such as chondrocytes, collagen and proteoglycan, are also change during this process.
OBJECTIVE: To compare the content changes of collagen, proteoglycan and the apoptosis of chondrocytes on two model groups of knee joint instability, additionally, to investigate the occurrence mechanism of early articular cartilages changes in rabbits with knee joint instability.
METHODS: A total of 50 white rabbits were randomly divided into anterior cruciate ligament transection group, medial collateral ligament transection + meniscectomy group and normal control group. The specimens were harvested at weeks 1, 2, 3, 4, and 5 after operation. The osteocartilaginous section of the medial femur condyles were observed by gross observation, histological examination, and Markin scores. The contents of proteoglycan and collagen fiber were also measured.
RESULTS AND CONCLUSION: Chondrocytes apoptosis were found with certain degrees at different stages of knee joint instability models. The Mankin score of the anterior cruciate ligament transection group was greater than the medial collateral ligament transection + meniscectomy group at each time point except the 1st week (P < 0.05), which was notably greater in the 5th week. At weeks 3 and 4 after operation, the chondrocytes degenerated with proteoglycan lost in the anterior cruciate ligament transection group, and the chondrocytes degeneration was predominant at 5th week. The changes were more seriously in the medial collateral ligament transection + meniscectomy group. Meantime, the collagen fiber content of two experimental groups were less than the normal control group at weeks 3, 4, 5 after operation (P < 0.05). The results demonstrated that at early knee joint instability, the articular cartilages degenerated extent is related to the number of chondrocytes, the collagen network disrupts and lost of proteoglycan. During chondrocytes degeneration, cartilage repair simultaneously occurred.