Immobilization induced effects in Articular Cartilage and their reversal on rembilization in rats

Background: Articular cartilage is a thin, smooth, low friction gliding surface with remarkable resiliency to compressive forces. Its mechanical and structural capacity is dependent on the integrity of its extracellular matrix. Effects of immobilization on articular cartilage has been studied in the past. This study was designed to observe inflammatory changes on immobilization and their reversibility on remobilization.Material Methods: Ninety male rats of same age were divided into groups and immobilized, remobilized and sacrificed at different periods. The knee joint was cut in sagittal plane and kept in 10% formalin for 48 hours. After processing 10μm sections were cut and stained with Alcian blue to demonstrate proteoglycan content.Results: Extensive necrotic changes were observed on 4 weeks immobilization. In four of the immobilized animals the entire articular cartilage was eroded. On 4 weeks immobilization staining character in superficial zone demonstrated mild staining in 76% while 24% specimens had lost staining with Alcian blue stain as compared to control group in which 100% specimens were mildly stained. In the group remobilized for 4 weeks, there were focal necrotic areas and splitting of cells from superficial zone.Conclusion: Immobilization leads to the development of necrosis, clefts and fissures. Remoblization for four weeks does not reverse the changes significantly