Effects of immobilisation and re-mobilisation on superficial zone of articular cartilage of patella in rats

Objective: to determine the staining grades and morphological changes in the cells of articular cartilage of patella on immobilisation and re-mobilisation in rats. methods: a total of 120 sprague dawley rats were divided into four groups of 30 animals. the study was done between july and december 2009. group i consisted of control animals that were not immobilised. group 2 wereimmobilised for four weeks. group 3 consisted of animals that were immobilised for four weeks and re-mobilised for four weeks. group 4 consisted of animals that were immobilised for four weeks and re-mobilised for eight weeks. at the end of the period, the knee joint was dissected in sagittal plane along with patella. tissue specimens were stored in 10% formalin for 48 hours. after processing for making paraffin blocks, 10>m and 7 >m sections were cut from the same block and stained with alcian blue and haematoxylin and eosin stain. results: extensive necrotic changes were observed on four weeks immobilisation. on four weeks remobilisation after four weeks of immobilization, the superficial zone was sloughed off, but on eight weeks remobilisation after four weeks of immobilization, regeneration was seen in the superficial zone. the superficial zone was affected both in immobilisation and re-mobilisation. conclusion: after eight weeks re-mobilisation, regeneration was still going on. no conclusion can be drawn regarding the exact time required for complete reversibility of the changes in the cartilage.