The articular cartilage can be divided into four distinct zones: a superficial (or tangential) zone, a transitional (or intermediate) zone, a deep (or radial) zone and a calcified cartilage zone. Each zone contains a distinct subpopulation of chondrocytes that differs in morphology, distribution within the matrix as well as metabolic activity. Articular cartilage of patella in rats consists of a highly organized matrix with a sparse population of highly specialized chondrocytes. The chondrocytes in the articular cartilage are surrounded by a specialized microenvironment, which effectively insulates the chondrocytes and physically separates the cell from direct interaction with the bulk of the load bearing matrix. The present study was conducted to see histological changes in pericellular matrix and also in chondrocytes by varying periods of immobilization. Methods: 30 male rats belonging to Sprague Dawley strai n were procured from National Institute of Health Islamabad and the study was carried out at the animal house College of Physician and Surgeons Islamabad. These animals were divided into three groups. The right hind limbs of rats were immobilized with plaster of Paris cast. Animals in these groups were immobilized, remobilized and sacrificed at different periods a given below. Group 1: Control group of 10 animals who were left un-immobilized. Group 2: Experimental group of 10 animals who were immobilized for two weeks. Group 3: Experimental group of 10 animals who were immobilized for four weeks. The skin over knee joint was dissected and the joint along with patella was exposed. The knee joint was cut in sagittal plane. It was stored in 10% formalin for 48 hours. After processing for making paraffin blocks sections were cut from the same block and stained with Alcian Blue and H&E stain. Result: In the group immobilized for two weeks in only th ree experimental animals the cells were like fibroblasts and no loss of staining was seen in the pericellular matrix in any of the experimental animal as compared to the control group. After four weeks immobilization the diffuse necrosis of chondrocytes, with pit formation on the surface and disruption loss of staining with Alcian Blue stain was seen to some extent in all the animals. Conclusion: The chondrocytes as well as the pericellular matrix of articular cartilage shows changes on immobilization and surface chondrocytes are vulnerable to immobilization injury.